Question

Which atom or ion is the largest? A. K B. K+ C. Ca D. Ca2+ E. Li

Answer 1

Hi!

I could go on about atomic size trends in the periodic table but there's a quicker method...

We know when the no of protons (+ charge) are greater than the no of electrons (- charge), the nucleus pulls the electrons with greater force, hence making the size smaller.

K has 19 protons, 19 electrons

K+ has 19 protons, 18 electrons

Ca has 20 protons, 20 electrons

Ca2+ has 20 protons, 18 electrons

Li has 3 protons, 3 electrons

Clearly, the cations are smaller than the atoms, this largest atom/ion will be Ca.

Answer 2

C. Ca atom is the largest.

About Atomic radius:

• The distance between an atom's nucleus and its outermost shell is measured in atomic size.
• In basic chemistry, the atomic radius is defined as the shortest distance between an atom's nuclei and its outermost shell.
• An atom's radius increases in direct proportion to its atomic number.
• The radius of each successive nearby atom rises as you proceed straight down a column on the periodic table.
• As you advance down the periodic table, the number of full electron shells increases, resulting in a larger size.
• The atomic radius of a group drops and grows over time in general.
• The number of energy levels (n) grows in a group downwards as the distance between the nucleus and the outermost orbital increases.
• As a result, the atomic radius is increased.

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