Which of the following pairs of atomic numbers belongs to the same group in the periodic table?

How many of the following statements are correct?
$(a)$ 'He' is the second most abundant element in the universe.
$(b)$ The symbol for the element with atomic number $110$ is Ds.
$(c)$ Osmium has the highest density among all elements.
$(d)$ Francium is the most electropositive element in the periodic table.

Which of the following statement$(s)$ is/are incorrect?

Select the correct statements from the following:
$(a)$ Effective nuclear charge for nitrogen is $3.90$
$(b)$ $IP$ of $Ne$ is more than $Na^{+}$
$(c)$ Order of electronegativity $sp > sp^2 > sp^3$
$(d)$ Order of acidic character $NH_3 < PH_3 < AsH_3$

Which has maximum $EA$,$EN$ and $IP$ respectively $:-$
$A = 1s^2 \ 2s^2 \ 2p^6$
$B = 1s^2 \ 2s^2 \ 2p^6 \ 3s^2 \ 3p^5$
$C = 1s^2 \ 2s^2 \ 2p^5$
$D = 1s^2 \ 2s^2 \ 2p^6 \ 3s^1$

Use the periodic table to answer the following questions.
$(a)$ Identify an element with five electrons in the outer subshell.
$(b)$ Identify an element that would tend to lose two electrons.
$(c)$ Identify an element that would tend to gain two electrons.
$(d)$ Identify the group having metal,non-metal,liquid as well as gas at room temperature.