how to find the valence electrons of any atom

Finding the valence electrons of an atom is essential for understanding its chemical behavior and its potential to form bonds with other atoms. Valence electrons are the electrons in the outermost energy level or shell of an atom. Here's how you can find the valence electrons of any atom:

Determine the Atomic Number

Look up the atomic number of the element you are interested in. The atomic number is typically found on the periodic table and is unique to each element.

Identify the Electron Configuration

You can find the electron configuration of an element using the periodic table or reference materials. The electron configuration tells you how the electrons are distributed in different energy levels or electron shells.

Count the Electrons in the Outermost Shell

• To find the valence electrons, focus on the electrons in the outermost energy level. This level is often referred to as the "valence shell."
• The number of electrons in the valence shell corresponds to the group number of the element on the periodic table. For example:
  • Group 1 elements (alkali metals) have 1 valence electron.
  • Group 2 elements (alkaline earth metals) have 2 valence electrons.
  • Group 13 elements have 3 valence electrons.
  • Group 14 elements have 4 valence electrons.
  • Group 15 elements have 5 valence electrons.
  • Group 16 elements have 6 valence electrons.
  • Group 17 elements (halogens) have 7 valence electrons.
  • Group 18 elements (noble gases) have 8 valence electrons, except for helium, which has 2 valence electrons.

Account for Transition Metals

Transition metals, found in the middle of the periodic table, have variable valence electrons. Their electron configuration may involve filling the d orbitals, and the number of valence electrons can vary depending on the specific element and its oxidation state. You may need to refer to a chemistry resource or table to determine the valence electrons for transition metals.

Consider Exceptional Cases

Some elements, like hydrogen and helium, do not fit the typical valence electron pattern because they have only one energy level. Hydrogen has 1 valence electron, and helium has 2 valence electrons.

By following these steps and referring to the periodic table, you can determine the number of valence electrons for most elements. Understanding the valence electrons of an atom is crucial for predicting its chemical reactivity and bonding behavior in chemical reactions.

Example

Each oxygen atom has the electron configuration 1s² 2s² 2p⁴ So Oxygen (O) has 6 valence electrons because outermost shell or energy level is 2 and in that energy level we have 2 and 4 electrons in s and p orbital respectively. So total electrons in the outermost shell is 6. Most of the students get confused with orbital and energy level. You need to note that s and p are orbitals in the same Energy Level (2) so we need to take addition of all electrons available in those orbitals.

So to just clarify again, In oxygen we have 2 energy levels - 1 and 2.

• Energy level 1 has 1 subshell s which can contain 2 electrons
• Energy level 2 has 2 subshells (orbitals) s and p each holding 2 and 4 electrons respectively.