Question

electron configurations

1. identify the block, period and group the following elements are found in on the periodic table. what is the electron configuration of the following elements?

a. be
b. mg
c. ca

Explanation:

Step1: Recall periodic - table basics for Be

Beryllium (Be) has atomic number 4. It is in the s - block as its outermost electrons are in the s - orbital. It is in period 2 and group 2. The electron configuration is determined by filling orbitals in the order of increasing energy.
$1s^{2}2s^{2}$

Step2: Recall periodic - table basics for Mg

Magnesium (Mg) has atomic number 12. It is in the s - block. It is in period 3 and group 2. Filling orbitals in order of energy, its electron configuration is $1s^{2}2s^{2}2p^{6}3s^{2}$.

Step3: Recall periodic - table basics for Ca

Calcium (Ca) has atomic number 20. It is in the s - block. It is in period 4 and group 2. Its electron configuration is $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}$.

Answer:

a. Block: s - block, Period: 2, Group: 2, Electron configuration: $1s^{2}2s^{2}$
b. Block: s - block, Period: 3, Group: 2, Electron configuration: $1s^{2}2s^{2}2p^{6}3s^{2}$
c. Block: s - block, Period: 4, Group: 2, Electron configuration: $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}$