Calculate the atomic number and number of p-electrons of an atom whose valance shell electronic configuration is 4s?

The electron whose valence shell electronic configuration 4s² may be Calcium(Ca).  The atomic number of calcium is 20. The electronic configuration of calcium is

Ca₂₀ = 1s², 2s² 2p⁶, 3s² 3p⁶, 4s²

The total number of p-electrons are 12.

Does a nucleus contain electrons ? Explain .

No, a nucleus does not contain electrons. Electrons are negatively charged subatomic particles that orbit the nucleus in specific energy levels or electron shells. The nucleus, on the other hand, is the central region of an atom that contains protons and neutrons tightly bound together. Protons are positively charged particles, and neutrons have no charge. The number of protons determines the atomic number of an element and defines its identity, while the number of neutrons can vary to form...

How many electrons and neutrons are present in the symbol 2713Al3+?

Atomic no. (Z) = 13 and atomic mass (A) = 27
No. of neutrons = A-Z = 27 - 13 = 14
No. of electrons = 13 - 3 = 10

Al atom loses 3e^- to form Al⁺³.

How do electrons interact with electromagnetic fields, and what are the consequences of such interactions in fields like optics and electronics?

Sodium and Mg+ ion have same number of electrons but removal of electron from Mg+ requires more energy than sodium. Explain. 

Ans: Though sodium and Mg⁺ ion have same number of electrons the atomic size of Mg⁺ is smaller than Na. Since, smaller the size, the greater is the nuclear force of attraction for valance electrons due to which removal of electron from Mg⁺ requires more energy than sodium.

What are valence electrons? What change in the valency observed while moving from left to right in a period?

The electrons present in the outermost shell or valence shell of an atom are called valence electrons.

In a period, valency increases up to the 4th group and decreases up to the 8th group and again increases.

Lone pairs of electrons present on an atom in any molecule affect its geometry. Explain with an example.