Question

write a complete chemical formula, including physical state symbol, for each element listed below in its standard state. the first row of the table has been completed for you. element formula iron fe(s) helium lanthanum hydrogen

Explanation:

Step1: Recall helium's standard - state

Helium is a noble gas. In its standard state, it is a monatomic gas.
$He(g)$

Step2: Recall lanthanum's standard - state

Lanthanum is a metal. In its standard state, it is a solid.
$La(s)$

Step3: Recall hydrogen's standard - state

Hydrogen exists as a diatomic molecule in its standard state and is a gas.
$H_2(g)$

Answer:

helium: $He(g)$
lanthanum: $La(s)$
hydrogen: $H_2(g)$