Chemistry questions! Pls Help~

Which is the most electronegative of the elements liste?

The answer is 4 (Cl).

When going down a group (other than Group 0), the electronegativity of the element is decreasing.

When going across a period (from left to right), the electronegativity of the element is increasing.

Since Cl is the second element of Group VII (the rightmost group), Cl is the most electronegative among the listed elements.

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Which of the following contains only covalent bonding and no ionic bonding?

The answer is 3 (CCl4).

A simple ionic bond is formed between a metal (or ammonium ion) and a non-metal (or a group of non-metals).

Covalent bonds are formed between non-metals.

Among the listed compounds, CCl4 contains only non-metals. However, other compounds contains both metals and non-metals.

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What distinguishes one element from another?

The answer is 4 (the number of protons).

The number of neutrons is incorrect. This is because atoms of the same elements may have different numbers of neutrons. Such atoms are called isotopes.

The number of electrons is incorrect. This is because atoms may gain or lose electrons when forming ionic compounds.

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How many protons are present in one Ca2+ ?

The answer is 3 (20).

The atomic number of Ca is 20. Each Ca atom contains 20 protons.

When a Ca atom changes to a Ca2+ ion, it loses 2 electrons but the number of protons is unchanged.
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