The central Xe atom in the XeF4 molecule has unbonded electron pair(s) and bonded electron pair(s) in its valence shell.

Lewis structure in attachment.

Explanation:

Atoms of elements in and beyond the third period of the  periodic table form some compounds in which more than eight electrons surround the  central atom. In addition to the 3s and 3p orbitals, elements in the third period also  have 3d orbitals that can be used in bonding. These orbitals enable an atom to form  an expanded octet.

The central Xe atom in the XeF₄ molecule has two unbonded electron pairs and four bonded electron pairs in its valence shell.

(newtons first law)

conservation of momentum law states :

momentum before collision = momentum after collision

momentum p (kg-m/s)= mass * velocity

say moving car=1 000 kg, velocity = 10 m/s then p = 1 000*10= 10 000 kg-m/s

say still car = 2 000 kg, velocity = 0 m/s then p = 2 000* 0 = 0 kg-m/s

total momentum prior to collision = 10 000 + 0 = 10 000 kg-m/s

momentum after collision = 10 000 kg-m/s

mass now = 1 000 kg+2 000 kg = 3 000 kg

10 000 = 3 000 kg* velocity m/s

10 000/3 000 = velocity

3.33 m/s = velocity after collision

an impulse is a force applied over time , momentum is exclusive of external forces and a perfect collision is implied