Calculate the mass of solid sodium that's needed to fully react with 4.0 l of chlorine gas at stp.
_na ₍s₎+_cl₂₍g₎ →_nacl₍aq₎

8.28g Na

Explanation: use ideal gas law

PV= nRT

Solve for moles of Cl2

n= PV/ RT

Substitute:

= 1 atm x 4.0 L / 0.08205 L.atm/ mol. K x 273 K

= 0.18 moles Cl2

Do stoichiometry to solve for m of Na

2 Na + Cl2 => 2 NaCl2

=0.18 moles Cl2 x 2 mol Na/ 1 mol Cl2 x 23g Na / 1 mol Na

= 8.28 g Na.

you need to take a look at the periodic system in order to sort these elements into pairs that would most likely exhibit similar chemical properties. first, you need to find elements that are found in the same group (groups are vertical in the periodic system), and then to see whether they have the same valence number. if they meet these criteria, they will have similar properties.

the first pair: ne (neon) and kr (krypton), are noble gases found in group 8

the second pair: li (lithium) and k (potassium), found in group 1

the third pair: s (sulfur) and te (tellurium), found in group 6