Fuse School - Periodic Table and Electron Configurations Quiz

What does the atomic number of an element represent?

• Number of protons in the nucleus

• Number of electrons in the nucleus

• Number of electron shells

• Number of neutrons in the nucleus

How many electrons can the first electron shell hold?

• 4

• 6

• 2

• 10

Answer explanation

The first electron shell can hold up to two electrons.

This is because the first shell has only one subshell, called the s subshell, which can accommodate a maximum of two electrons.

The first shell is also the closest to the nucleus and has the lowest energy level^.

What is the electron configuration of a helium atom?

• 2 in the first shell

• 2 in the third shell

• 2 in the second shell

• 1 in the first shell and 1 in the second shell

Answer explanation

The electron configuration of a helium atom is

1s2

or [He] in shorthand notation.

This means that helium has two electrons in its 1s orbital, which is the lowest energy level and the closest to the nucleus. Helium is a noble gas and has a full outer shell of electrons, making it very stable and unreactive.

What is the number of valence electrons for nitrogen?

• 5

• 4

• 6

• 3

How many electron shells do the elements in the second period have?

• 4

• 3

• 2

• 1

Answer explanation

The period of the periodic table indicates the number of electron shells that an element has¹². For example, elements in the first period have one electron shell, elements in the second period have two electron shells, and so on³⁴.

The number of electron shells affects the size and reactivity of the atoms.

What is the electron configuration of potassium?

• 2 in the first shell

• 1 in the fourth shell

• 8 in the third shell

• 8 in the second shell

Answer explanation

The electron configuration of potassium is

1s2 2s2 2p6 3s2 3p6 4s1

or [Ar] 4s1 in shorthand notation¹².

This means that potassium has a total of 19 electrons, with two in the 1s orbital, two in the 2s orbital, six in the 2p orbital, two in the 3s orbital, six in the 3p orbital, and one in the 4s orbital³.

If you want to learn more about electron configurations, you can check out these links:

• Electron Configuration Chart of All Elements (Full Chart)

• How to Write the Electron Configuration for Potassium (K)

• Potassium Electron Configuration:9 Facts You Should Know! - Lambda Geeks

What does the number of valence electrons correspond to in the periodic table?

• Group number

• Atomic number

• Atomic mass

• Period number

How many electron shells do the elements in the third period occupy?

• 1

• 2

• 3

• 4