Simple atomic structure for home learningAtomic number, mass number and electron arrangement. Check your learning with a 30 second 5 question quiz
Atomic Number and Mass Number.
- The atomic number is the number of protons in the nucleus of an atom.
- In a neutral atom the numbers of protons (+) and electrons (-) are the same.
- The mass number is the total number of protons and neutrons in the nucleus of an atom.
But wot about the electrons?
- Electrons are arranged in cloud like shells around the nucleus.
- Shells closest to the nucleus fill up with electrons first.
- The first shell is full with two electrons.The second and third shells are full with eight electrons.
- For the first twenty elements remaining electrons go in the fourth shell.
The sodium atom
- the atomic number is 11. There are 11 protons in the nucleus and eleven electrons in the shells around the nucleus.
- Two electrons go in the first shell, eight in the second and the remaining electron goes in the third shell.
- The electron configuration for sodium is Na(2,8,1). This is enough information to understand how the first 20 elements in the periodic table react with each other,