how to find number of electrons

Question

There are two main ways to find the number of electrons in an atom:

Answer 1

1. Using the Periodic Table:

The periodic table is a fantastic resource for finding the number of electrons in an atom. Here's how:

• Look up the element you're interested in on the periodic table.
• Each element has an atomic number displayed in the upper left corner of its square.
• The atomic number directly represents the number of protons in a neutral atom, and for neutral atoms, the number of protons equals the number of electrons.

Therefore, the atomic number tells you how many electrons a neutral atom of that element has.

2. Considering Ion Charge (Optional):

• This method applies when you're dealing with ions, which are atoms that have gained or lost electrons.
• If the atom is a positively charged ion (cation), it has lost electrons. The number of electrons lost will be equal to the positive charge of the ion.
• Conversely, if the atom is a negatively charged ion (anion), it has gained electrons. The number of electrons gained will be equal to the negative charge of the ion.

Here's the formula to find the number of electrons in an ion (considering you know the neutral atom's electrons and the ion's charge):

• Number of Electrons in Ion = Number of Electrons in Neutral Atom ± Charge of the Ion

Example:

• Find the number of electrons in a Carbon (C) atom.

  • Look up Carbon on the periodic table. Its atomic number is 6.
  • Therefore, a neutral carbon atom has 6 electrons (protons and electrons are equal in a neutral atom).

• Find the number of electrons in a Sulfur (S) ion with a charge of -2 (Sulfide ion).

  • Look up Sulfur on the periodic table. Its atomic number is 16.
  • A neutral sulfur atom has 16 electrons.
  • Since the ion has a -2 charge (meaning it gained 2 electrons), apply the formula:
    • Number of Electrons in Ion (Sulfide) = 16 (neutral atom) + (-2) (charge)
    • Number of Electrons in Ion (Sulfide) = 18

By understanding these methods, you can easily find the number of electrons in neutral atoms and various ions.