Why is the reaction of ethene with bromine called an addition reaction

Which type of orbits are found in the principal energy level n = 2 a - s b - s, f c - s, d d - s, p e - s, p, d

The table lists pressure and volume values for a particular gas. which is the best estimate for the value of v at p = 7.0 × 103 pascals?

Calculate the molar mass of aluminum oxide (al2o3). express your answer to four significant figures.