2.02 Periodic Trends (2023)


Valence Electrons

Periodic trends, or patterns in the periodic table, are prevalent all throughout the periodic table. It is important to note here that these patterns and trends we will be discussing are most clearly seen in the main group elements (elements in Groups 1-2 and 13-18).

Groups 3-12 do not follow the periodic patterns and trends as easily. This has to do with the way their electrons are arranged in the atom, but you will learn more about that in a chemistry course one day!For now, just realize when we talk about a pattern or trend, we are talking about the main group elements.

2.02 Periodic Trends (1)

(Video) 2.02 Periodic Table Terminology

The first pattern we will discuss are valence electrons. Valence electrons are the outer most electrons in an atom. They are the ones that are furthest from the nucleus.

2.02 Periodic Trends (2)

The electrons in the outer ring of this atom are the valence electrons.

In our example image above, the electrons are shown in different energy levels. The electrons that are in the level furthest from the nucleus are considered valence electrons. So, this atom has 7 valence electrons.

(Video) Chemistry Tutorial 2.02a: Basic Properties Of Element Types

Valence electrons are important because, since they are the outermost electrons, they are the electrons that interact with other atoms. Therefore, they are responsible for most of the properties (characteristics or behaviors) of an atom. In general, an atom can have from 1-8 valence electrons.

2.02 Periodic Trends (3)

Look at the different elements shown above. They each have different numbers of valence electrons (circled in yellow on the image). See a larger version of the image here.

Pattern of Valence Electrons

Let's examine the pattern of valence electrons in the Periodic Table.

(Video) Chemistry Tutorial 2.02c Metallic and Nonmetallic Character

2.02 Periodic Trends (4)

See a larger version of the periodic table here.

The number of valence electrons for each element actually varies directly with the group the element is in. The group number helps indicate the number of valence electrons. Review the list below to see this pattern:

  • Group 1 has 1 valence electron.
  • Group 2 has 2 valence electrons.
  • Group 13 has 3 valence electrons.
  • Group 14 has 4 valence electrons.
  • Group 15 has 5 valence electrons.
  • Group 16 has 6 valence electrons.
  • Group 17 has 7 valence electrons.
  • Group 18 has 8 valence electrons.

Notice that we skipped Groups 3-12. Again, it's because these groups do not follow the predicted patterns well.

(Video) Periodic Trends

The periodic trend of the number of valence electrons being linked to an element's group number only works for Groups 1-2 and 13-18.

How to Determine

To find the number of valence electrons, we simply determine what group an element is in. For example, the element sodium (Na) has 1 valence electron because it is in Group 1.

Now you try. How many valence electrons does sulfur (S) have?

Answer: Sulfur has 6 valence electrons because it is in Group 16. Remember, don't confuse valence electrons with total electrons! Sulfur has 14 total electrons (based on its number of protons) and then 6 of these are valence electrons.

(Video) 2.02 Mad Scientist Disruption & the FOE - Accurate Technology Forecasting Dr Alexander


How many valence electrons are in Group 2? ›

Group 2 has 2 valence electrons.

What is the Valency of Group 2? ›

Thus, the element in the second group of the periodic table will have an outermost s orbital filled with two electrons of different spins. Hence, the number of valence electrons in group 2 is two.

What are the periodic trends for valence electrons? ›

Trend-wise, while moving from left to right across a period, the number of valence electrons of elements increases and varies between 1 to 8. But the valency of elements first increases from 1 to 4, and then it decreases to zero as we reach the noble gases.

Which group tends to form +1 ions? ›

The alkali metals will lose an electron to resemble the next lowest noble gas; thus, all the alkali metals form +1 ions.

What is group 2 on the periodic table called? ›

Group 2A (or IIA) of the periodic table are the alkaline earth metals: beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra).

How many electrons can group 2 hold? ›

Each p orbital can hold two electrons. Therefore, the second energy level can hold a maximum of eight electrons.

What is the trend of group 2 elements? ›

Melting Point Trend Down Group 2. As you move down Group 2, the melting points of the elements decreases. Group 2 elements generally have metallic bonding as they are metallic structures. As you move down the group, the radius of the metal ions increases but the number of delocalised electrons stays the same per atom.

Why is Group 2 in the periodic table? ›

The elements that are in group 2 of the periodic table are called alkaline earth metals. They are called alkaline metals as they form an alkaline solution when mixed with water.

What is the symbol of Group 2? ›

They are beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra). Was this answer helpful?

How do you find periodic trends? ›

Moving left to right on the periodic table causes an increase in atomic number (number of protons) as well as electron affinity and electronegativity. Atomic radius, however, will decrease when moving left to right. As more protons are added to the nucleus, they have a stronger attraction to the electrons.

What is a periodic trend examples? ›

Major periodic trends include: electronegativity, ionization energy, electron affinity, atomic radius, melting point, and metallic character.

What are the 4 periodic trends? ›

Periodic trends are patterns in elements on the periodic table. Major trends are electronegativity, ionization energy, electron affinity, atomic radius, and metallic character.

Which will form an ion with a +2 charge? ›

Alkaline earth metals have 2 electron in their outermost orbital,after donating these two electron stable state can be achieved with fully occupied outermost orbital. so Alkaline earth metals can form ions with a 2+ charge.

What group forms +2 ions? ›

The alkaline earth metals (red) always form +2 ions. The halogens (blue) always form -1 ions.

Which of these elements is most likely to form ions with a 2+ charge? ›

Answer and Explanation: The elements most likely to form an anion with a charge −2 are Group 6 elements.

What does +2 mean in the periodic table? ›

Helium is the element that is atomic number 2 on the periodic table. Each helium atom has 2 protons in its atomic nucleus. The atomic weight of the element is 4.0026.

What is 2 on the periodic table? ›

Helium - Element information, properties and uses | Periodic Table.

Are group 2 elements bases? ›

Group 2 hydroxides and carbonates are bases, and are often used as antacids to treat acid indigestion (an excess of hydrochloric acid in the stomach) by neutralisation.

What can hold only 2 electrons? ›

Orbital: A region of space within an atom where an electron in a given subshell can be found. Any orbital can hold a maximum of 2 electrons with opposite spin.

How many group 2 elements are there? ›

The alkaline earth metals are six chemical elements in group 2 of the periodic table. They are beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra).

What element only has 2 electrons? ›

So... for the element of HELIUM, you already know that the atomic number tells you the number of electrons. That means there are 2 electrons in a helium atom.

What happens down group 2? ›

In moving down Group 2 there is an additional quantum shell of electrons for each element. The effect of this is that the outer electrons are increasingly shielded from the attraction of the nucleus so the overall nuclear attraction on the outermost electrons is less resulting in an increase in atomic radius.

How do group 2 elements react? ›

Group 2 elements react readily with dilute acids to form a salt and hydrogen. The reaction between a Group 2 element and oxygen is a redox as Group 2 elements are oxidised from an oxidation state of 0 to +2 and hydrogen is reduced from a +1 state to 0. Reactivity increases down the group.

What is trend in reactivity down group 2? ›

The reactivity of the group 2 elements increase as you go down the group. This is because, as explained previously, it is much easier to remove an outer shell electron as you go further down the group (lower ionisation energies).

Why will group 2 atoms form +2 ions? ›

In this case elements located in group 2 will always lose electrons to become cations. Basically they will lose 2 electrons to form cations with charge of +2. Hence Group 2A elements form ions by losing two electrons.

Which group 2 element is most active? ›

Complete answer: Beryllium: Beryllium is a chemical compound of group two which is donated by symbol Be. Atomic number of beryllium is four.

Is group 2 only metals? ›

The Group 2 elements are all metals with a shiny, silvery-white colour. The alkaline earth metals are high in the reactivity series of metals, but not as high as the alkali metals of Group 1.

Is Group 2 positive or negative? ›

Group 1 and 2 elements are metals and they lose/ give electrons resulting in them becoming positive ions (they become cations). Group 6 and 7 elements are non-metals and they receive/ gain electrons resulting in them becoming negative ions (they become anions).

Why is Group 2 reactive? ›

Alkaline Earth metals are very reactive because they readily give up their two valence electrons to achieve a full outer energy level, which is the most stable arrangement of electrons.

What are the trends in the periodic table answers? ›

There are four main periodic trends: electronegativity, atomic size, ionization energy, and electron affinity.

How do you calculate a periodic number? ›

The period of an element is represented by the principal quantum number (n) of the valence electrons in the electronic configuration of an atom. The number of shells equals the number of periods when determining a period. Example: Na- 2,8,1 - There are three shells, hence the period number is 3.

How do you calculate periodic signals? ›

Periodic Functions

x(t) = x(t + nT). The minimum value of T that satisfies x(t) = x(t + T) is called the fundamental period of the signal and we denote it as T0. Examples of periodic signals are infinite sine and cosine waves. Examples: Given x1(t) = cos(3t), and x2(t) = sin(5t).

What does periodic trend mean? ›

A periodic trend is a regular variation the properties of an element with increasing atomic number. A periodic trend is attributed to regular variations in the atomic structure of each element.

What is the three example of trend? ›

The three main types of trends are uptrends, downtrends and horizontal trends.

What is a periodic trend quizlet? ›

Periodic trends. The tendencies of certain properties to increase or decrease as you move across a period or down a group. - A.k.a. patterns on the periodic table.

What are trends in periodic table grade 11? ›

Periodic trends are those which explain certain properties of elements that are present in the periodic table. The periodic trends are atomic radii, ionic radii, ionisation energy, electron gain enthalpy, electronegativity, metallic character, etc.

What is a +2 ion? ›

There are additional names used for ions with multiple charges. For example, an ion with a −2 charge is known as a dianion and an ion with a +2 charge is known as a dication. A zwitterion is a neutral molecule with positive and negative charges at different locations within that molecule.

How is a 2+ ion formed? ›

Ion Formation Patterns

In general, atoms form ions according to the following patterns: Metals in Group 1 have only one electron in their valence shell. They can give up this one electron and become 1+. Group 2 elements give up two electrons to become 2+, and Group 3 give up three electrons to become 3+.

Does o form a +2 ion? ›

The element oxygen has six valence electrons. To fill up the valence shell the oxygen atom needs two more electrons. As every electron has a single negative charge, adding two more electrons gives oxygen ion a charge of 2 .

Can you form 2+ and 3+ ions? ›

Thus, Iron can form 2+ and 3+ ions.

What metal only forms 2+ ions? ›

As an example, iron commonly forms two different ions. It can sometimes lose two electrons to form the Fe2+ ion, while at other times it loses three electrons to form the Fe3+ ion. Tin and lead, though members of the p block rather than the d block, also are capable of forming multiple ions.

Which of the following element has a charge of +2 positive two )? ›

He has 2 electrons and 2 protons. After donating these two electrons it forms 2+ charge stable ion.

How many valence electrons are in Group 3? ›

The Group 3A metals have three valence electrons in their highest-energy orbitals (ns2p1). They have higher ionization energies than the Group 1A and 2A elements, and are ionized to form a 3+ charges. The Group 3A metals are silvery in appearance, and like all metals are good conductors of electricity.

How many valence electrons are in Group 4? ›

For example, carbon is in group 4 and has 4 valence electrons. Oxygen is in group 6 and has 6 valence electrons.

What group has 7 valence electrons? ›

The Group 7A elements have seven valence electrons in their highest-energy orbitals (ns2np5). This is one electron away from having a full octet of eight electrons, so these elements tend to form anions having -1 charges, known as halides: fluoride, F-; chloride, Cl-, bromide, Br-, and iodide, I-.

What element has 2 valence electrons? ›

*Note that helium (He) only has two valence electrons.

Do valence electrons have 1 or 2? ›

An atom with a closed shell of valence electrons (corresponding to a noble gas configuration) tends to be chemically inert. Atoms with one or two valence electrons more than a closed shell are highly reactive due to the relatively low energy to remove the extra valence electrons to form a positive ion.

What is the 2 8 8 18 rule in chemistry? ›

Each shell can contain only a fixed number of electrons: the first shell can hold up to two electrons, the second shell can hold up to eight (2 + 6) electrons, the third shell can hold up to 18 (2 + 6 + 10) and so on. The general formula is that the nth shell can in principle hold up to 2(n2) electrons.

What has 2 electron shells and 3 valence electrons? ›

Boron is the element which has a total of two shells, with three electrons in its valence shell.

What has 2 valence electrons and 3 shells? ›

∴ Element = Magnesium. Was this answer helpful?

What element has 5 valence electrons? ›

Elements having 5 valence electrons are placed in Group 15. The elements of group 15 are nitrogen, phosphorus, arsenic and antimony.

What atom has 4 shells and 2 valence electrons? ›

Means Calcium is an element which lies at Period 4 in Periodic table and having two valence electrons (Period 4 means 4th shell being occupied having 2 electrons in 4th or outermost shell)

What element has 13 valence electrons? ›

Electron Configuration of Aluminum

Since aluminum's atomic number is thirteen, it has thirteen electrons.

Does nickel have 2 or 10 valence electrons? ›

Therefore, we can say that nickel has two valence electrons.

What group of elements has a charge of 2+? ›

The group that has elements with a 2 charge is alkali earth metals (group 2). Almost all the metals in the alkaline earth group can donate their two outermost electrons in order to form cations having a 2+ charge.

What family has 1 valence electron? ›

The alkali metals have only one valence electron in their highest-energy orbitals (ns1).

What are Group 8 elements called? ›

Group 8A (or VIIIA) of the periodic table are the noble gases or inert gases: helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). The name comes from the fact that these elements are virtually unreactive towards other elements or compounds.


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