Question

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)

Answer 1

carbon (C) and lead (Pb) 4e⁻

C [He]2s²2p²

Pb [Xe]6s²4f¹⁴5d¹⁰6p²

Answer 2

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

Step-by-step 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 :
`1s^22s^22p^4`

Electronic configuration of Bromine :
`[Ar]4s^23d^(10)4p^5`

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

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

Electronic configuration of Selenium :
`[Ar]4s^23d^(10)4p^4`

Electronic configuration of Bromine :
`[Ar]4s^23d^(10)4p^5`

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

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

Electronic configuration of Carbon :
`1s^22s^22p^2`

Electronic configuration of Lead :
`[Xe]6s^25d^(10)6p^2`

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

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

Electronic configuration of Oxygen :
`1s^22s^22p^4`

Electronic configuration of Carbon :
`1s^22s^22p^2`

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

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

Electronic configuration of Sodium :
`1s^22s^22p^63s^1`

Electronic configuration of Carbon :
`1s^22s^22p^63s^2`

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

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