Oxidation States and Oxides

O2 is the molecular formula for oxygen, a diatomic gas essential for respiration and combustion. Phosphorus is P4 in its white form, Oxide is a class of compounds (not a specific substance), and Bromide refers to bromine compounds (Br-). Oxygen makes up about 21% of Earth's atmosphere.

PbSO3 is Lead(II) sulfite - Pb is Lead, SO3 is the sulfite ion (not sulfate), and the +2 charge balances with the sulfite ion. Options A, B, and C are incorrect - option C contains a typo (sulpahte).

Fe(OH)2 is Ferrous hydroxide, where iron is in the +2 oxidation state (Fe2+). The term 'ferrous' specifically refers to Fe2+, while 'ferric' refers to Fe3+.

According to common brand etymology, EXIDE is said to stand for 'Excellent Oxide' in reference to battery technology, though this claimed expansion may be apocryphal. The other variations (Exclusive, Exact, Energetic) are not recognized as the brand's name origin.

Oxygen is the odd one out because it is a non-metal, while Sodium, Lead, and Iron are all metals. Metals are typically shiny, malleable, and good conductors of electricity, whereas oxygen is a gas that is a poor conductor.

Magnesium reacts with oxygen to form magnesium oxide (MgO) in a combination reaction. This is a classic example of a metal combining with oxygen. Iron would form iron oxide (rust), and the generic term 'metal' is too vague.

K2Cr2O7 is potassium dichromate, with two K+ ions and one Cr2O7 2- ion. The dichromate ion is Cr2O7 2-, distinct from chromate (CrO4 2-). Potassium chromate would be K2CrO4. The name dichromate indicates two chromium atoms in the anion.

Ag2SO4 is silver sulfate, composed of silver ions (Ag+) and sulfate ions (SO4 2-). The charges balance: two Ag+ ions (+2 total) with one SO4 2- ion (-2). Silver sulfite would be Ag2SO3, and the option D also contains a typo in 'siver'.

Chromium(II) indicates Cr^2+ ion. Nitrate is NO3^- with a -1 charge. To balance the +2 charge of chromium, two nitrate ions are needed, giving the formula Cr(NO3)2. Parentheses are required around NO3 to show two complete nitrate groups.

Beryllium has a +2 charge (Be^2+). Nitrate is NO3^- with a -1 charge. Two nitrate ions are needed to balance the +2 charge of beryllium, giving Be(NO3)2. Option D is correct.

Manganese(IV) indicates Mn^4+ ion. Sulfate is SO4^2- with a -2 charge. To balance the +4 charge of manganese, two sulfate ions are needed, giving Mn(SO4)2. Option B is correct.

Nickel(II) means Ni2+. Nitrite is NO2- with a -1 charge. To balance +2 and -1, you need two nitrite ions: Ni(NO2)2. Ni(NO2)3 would give -3, and the formulas for B and C don't balance charges.

Zinc(II) is Zn2+. Nitrite (NO2-) has a -1 charge. Two nitrite ions are needed to balance the +2 charge, giving Zn(NO2)2. Option B would give Zn4+ which doesn't exist, and Zn2NO2 doesn't balance.

Copper (Cu) is a metal that forms a basic oxide (CuO) when reacted with oxygen. Nonmetals like Nitrogen, Hydrogen, and Carbon form acidic or neutral oxides, while metals typically form basic oxides.