Question

1. which of the following groups contains elements that are most reactive metals?

a) group 1 (alkali metals)
b) group 17 (halogens)
c) group 18 (noble gases)
d) group 2 (alkaline earth metals)

1. the effective nuclear charge increases across a period because:

a) electrons are lost
b) energy levels are added
c) protons are added to the nucleus without much shielding
d) electrons are added to inner shells

1. which of the following has the largest atomic radius?

a) mg
b) ca
c) sr
d) ba

Explanation:

1. Alkali metals in Group 1 have one valence - electron which is easily lost, making them highly reactive metals. Halogens are non - metals, noble gases are inert, and alkaline earth metals are less reactive than alkali metals.
2. As we move across a period, protons are added to the nucleus while the shielding effect by inner - shell electrons does not increase significantly. This leads to an increase in effective nuclear charge.
3. Atomic radius increases down a group as new energy levels are added. Among Mg, Ca, Sr, and Ba which are in the same group (Group 2), Ba is at the bottom of the group and has the largest atomic radius.

Answer:

1. A. Group 1 (Alkali Metals)
2. C. Protons are added to the nucleus without much shielding
3. D. Ba