4. Express the answers to the following problems in scientific notation. Hint: Use the subtraction example to solve the addition problem. A. (1.8 X 1020) X (2.5 X 10^16) C. (9.2 X 10^19) ÷ (3.0 X 10^7) B.(7.9 X 10^9) - (6.0 X 10^8) D. (4.2 X 10^9) + (8.0 X 10^18)

2. you__turn left on a red light if you are in the left-most lane of a one-way street, you're turning into the left-most lane of a one-way street, and no nearby sign prohibits the turn.

Need ! asap will mark 10 pts using the room temperature line (orange line) and your periodic table, make lists that identify the state of matter (gas, liquid, or solid) in which each element you plotted exists at room temperature. explain your answers

Consider hydrogen in an excited state n = 5n=5 that emits photons to reach the ground state. there are various possible transitions other than straight to the ground state that can occur; for example, it can drop to the n = 3n=3 state followed by the n = 3n=3 to the ground state transition. which of the possible transitions will result in the emission of a photon in the visible region?