1b.6 Electron configurations

Question 1

HOw are electrons arranged in atoms?

Answer 1

In shells (also known as “energy levels”)

The electron shells with lowest energey (cloest to the nucleus) are filled first.

There is a limit to the number of electrons allowed in each shell

Question 2

How many electrons can the first three shells hold?

Answer 2

Shell 1 - 2 electrons

Shell 2 - 8 electrons

Shell 3 - 8 electrons

Question 3

What form of electron shells makes atoms the most stable?

Answer 3

Full outer electrons shells are the most stable (noble gases)

Otherwise, atoms try to react to fill (or empty) the outer shell

Question 4

What is meant by the electronic configuration of an atom?

Answer 4

It is a model of how the electrons of an atom are arranged

Question 5

How do you construct an electronic configuration diagramatically?

Answer 5

1. IDentify the number of electrons in the atom (=atomic number)
2. Draw the first shell and add (up to) 2 electrons
3. Draw the second shell and add (up to) 8 electrons
4. If needed, draw the third shell and add (up to) 8 electrons
5. Stop when yo uhave used up all the electrons

Note, in the first shell, draw the two electrons oppositve each other

In the 2nd/3rd shells, first draw one electron in each quadrant, then start pairing up (so a full shell has four pairs of electrons)

Question 6

How do you write down an electronic configuration?

Answer 6

As numbers separated by dots - the number of electrons in the first shell, then the 2nd etc.

E.g. nitrogen (7 electrons) is written as: 2.5

E.g. Aluminium (13 electrons) is written as: 2.8.3

Question 7

How do you work out an electronic configuration of an elemenet based on its position in the periodic table?

Answer 7

Period - number of shells. All these shells will be full EXCEPT the last one

Group - the last shell has the same number of electrons are the group number.