Which of these pairs of elements have the same number of valence electrons?
oxygen (o) and bromine (br)
selenium (se) and bromine (br)
carbon (c) and lead (pb)
oxygen (o) and carbon (c)
sodium (na) and magnesium (mg)

The correct answer is Carbon (C) and Lead (Pb)

Explanation:

Valence electrons is defined as the electrons which are present in the outermost shell of the element.

For the given options:

Option 1: Oxygen (O) and Bromine (Br)

Electronic configuration of Oxygen :

Electronic configuration of Bromine :

Oxygen has 6 valence electrons and bromine has 7 valence electrons.

Option 2: Selenium (Se) and Bromine (Br)

Electronic configuration of Selenium :

Electronic configuration of Bromine :

Selenium has 6 valence electrons and bromine has 7 valence electrons.

Option 3: Carbon (C) and Lead (Pb)

Electronic configuration of Carbon :

Electronic configuration of Lead :

Carbon has 4 valence electrons and lead also has 4 valence electrons.

Option 4: Oxygen (O) and carbon (C)

Electronic configuration of Oxygen :

Electronic configuration of Carbon :

Oxygen has 6 valence electrons and carbon has 4 valence electrons.

Option 5: Sodium (Na) and Magnesium (Mg)

Electronic configuration of Sodium :

Electronic configuration of Carbon :

Sodium has 1 valence electrons and magnesium has 2 valence electrons.

From the above information, the correct answer is Carbon (C) and Lead (Pb)

ca has a crystalline lattice with positive ions (since it is a metal, metals are positively charged) and electrons flow freely in its structure since the ca atoms have a large nuclear radius so the electrons are not tightly held, therefore the electrons can flow freely since they are not being highly attracted by the nucleus. moreover, one of the properties of metals are that they are conductors of electricity, thus proving ca is the element.