Question

An element has electronic configuration 2, 8, 1. Now answer the following questions.

a) Identify this element and write its atomic number.

b) To which period does this element belong?

c) With which of the following elements would this element resemble? (atomic numbers of the elements are

given in the brackets)

N(7), Be(4), Ar(18), Cl(17)​

Answer 1

Answer:

a) The element is Sodium and its Atomic number is 11

b) Sodium belongs to 3rd period

c) Be

Answer 2

Answer:

a) The electronic configuration 2, 8, 1 indicates that the element has 2 electrons in its first energy level (in the 1s orbital), 8 electrons in its second energy level (in the 2s and 2p orbitals), and 1 electron in its third energy level (in the 3s orbital). This corresponds to the electronic configuration of sodium (Na).

The atomic number of sodium is 11, which is the number of protons in its nucleus and also the number of electrons in its neutral state.

b) Sodium belongs to the third period of the periodic table because it has electrons in the third energy level.

c) Sodium (Na) would resemble chlorine (Cl) because they both belong to the same group (group 1) of the periodic table, which means they have similar chemical properties due to having the same number of valence electrons (1).

• On the other hand, nitrogen (N) and beryllium (Be) belong to different groups and have different numbers of valence electrons, so they would not resemble sodium as closely. Argon (Ar) is a noble gas and does not react chemically with other elements, so it would not resemble sodium either.

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