Answer:
Name Atomic Number Electron Configuration Period 1 Hydrogen 1 1s1 Helium 2 1s2 Period 2 Lithium 3 1s2 2s1 Beryllium 4 1s2 2s2 Boron 5 1s2 2s22p1 Carbon 6 1s2 2s22p2 Nitrogen 7 1s2 2s22p3 Oxygen 8 1s2 2s22p4 Fluorine 9 1s2 2s22p5 Neon 10 1s2 2s22p6 Period 3 Sodium 11 1s2 2s22p63s1 Magnesium 12 1s2 2s22p63s2 Aluminum 13
Answer:

Explanation:
Given that,
The dimension of a square chunk of plastic is 5 cm × 5 cm × 5 cm
Mass, m = 200 g
We need to find its density
Density = mass/volume
It will form a cube. It volume = side³
So,

Hence density is 
Answer:
pH = 7.46
Explanation:
2H₂O ⇄ H₃O⁺ . OH⁻ Kw = [H₃O⁺] . [OH⁻]
[H₃O⁺] = [OH⁻]
√0.12×10⁻¹⁴ = [H₃O⁺] → 3.46×10⁻⁸ M
- log [H₃O⁺] = pH
- log 3.46×10⁻⁸ = pH → 7.46