1. Subscript is below
2. Coefficient large 2 indicates the number of moles
3. Atoms
1/2 O2 + H2 —> H2O
It’s the atoms that balance on each side
Notes that 1/2 is the coefficient and 2 is the subscript in H2 and H2O
Answer:
A. Metalloid
E. Has similar properties as Ge
F. Belongs to Period 3
Explanation:
Silicon is the 14th element on the periodic table. Its unit is SI. Its properties straddles between those of metals and non-metals and it is described as a non-metal.
It's atomic weight or mass number is 28u. It has an atomic number of 14 i.e in its neutral state, the number of protons and electrons are equal to 14.
Silicon belongs to the 4th group and the 3rd period on the periodic table. Elements in the same group share similar chemical properties. The elements in Si group are: C, Ge, Sn and Pb. The properties of Si is similar to these elements because they all have a valency of 4. Across the period, the properties varies this is why Si would have a very different property from Al and P.
Answer: Transition from X to Y will have greater energy difference.
Explanation: For studying the energy difference, we require Planck's equation.

where, h = Planck's Constant
c = Speed of light
E = Energy
= Wavelength of particle
From the equation, it is visible that the energy and wavelength follow inverse relation which means that with low wavelength value, energy will be the highest and vice-versa.
As electron A falls from X-energy level to Y-energy level, it releases blue light which has low wavelength value (around 470 nm) which means that it has high energy.
Similarly, Electron B releases red light when it falls from Y-energy level to Z-energy level, which has high wavelength value (around 700 nm), giving it a low energy value.
Energy Difference between X-energy level and Y-energy level will be more.