Question

fill in the missing information about the atoms in the table below.

symbol	number of protons	number of electrons	number of electron shells
ba
ca
	total	valence

Explanation:

Step1: Recall atomic number concept

The number of protons is equal to the atomic number.

Step2: For Radium (Ra)

The atomic number of Ra is 88. So number of protons = 88. In a neutral atom, number of electrons = number of protons, so total electrons = 88. The electron - configuration of Ra is [Rn] 7s², so valence electrons = 2 and number of electron - shells = 7.

Step3: For Barium (Ba)

The atomic number of Ba is 56. So number of protons = 56. In a neutral atom, number of electrons = number of protons, so total electrons = 56. The electron - configuration of Ba is [Xe] 6s², so valence electrons = 2 and number of electron - shells = 6.

Step4: For Calcium (Ca)

The atomic number of Ca is 20. So number of protons = 20. In a neutral atom, number of electrons = number of protons, so total electrons = 20. The electron - configuration of Ca is [Ar] 4s², so valence electrons = 2 and number of electron - shells = 4.

Answer:

symbol	number of protons	number of electrons total	number of electrons valence	number of electron shells
Ba	56	56	2	6
Ca	20	20	2	4