<u>Answer 2 :</u> The given electronic configuration for a neutral atom of phosphorous in its ground state is incorrect.
Explanation :
A neutral atom of phosphorous has 15 electrons.
The given electronic configuration is incorrect.
The reason is, According to Aufbau principle, the electrons will be first filled in the sub-shell having lower orbital energy. As from the given configuration, 3p sub-shell has lower orbital energy than 4s sub-shell. So, the electrons will be filled in 3p sub-shell first. Hence, the ground state electronic configuration of neutral atom of phosphorous is,

<u>Answer 3 :</u>
Element Rubidium Magnesium Aluminium
Symbol Rb Mg Al
Group number 1 2 13
Number of valence 1 2 3
electrons
The order of general reactivity on the basis of number of valence electrons.
Rb > Mg > Al
Reason : The reactivity is determined by the number of electrons present in the outermost shell that means the element which have 1 valence electron will be more reactive because they can easily lose electrons.
Sodium would form Na+
Oxygen would form O-2
Phosphorus would form -3 or +5
Sodium and oxygen would combine to form ionic bonds because one is a metal and the other is non-metal, while Phosporus and oxygen would combine to form covalent bonds because they are both non-metals.
Answer is: density of the substance, energy of the substance, intermolecular bonds between particles.
Melting is a physical change (process), the same substance is present before and after the change, so chemical bonds and melting point of the substance are not changed.
Density of liquids are usually less than in solids, because atoms are further apart.
Liquids have higher energy and atoms or molecules move faster.
Intermolecular bonds are weaker in liquids.