Which of the following is correct? 1. The principal quantum number, n, describes the shape of an atomic orbital.
2. No more than two electrons in an atom can have the same principal quantum number (n).
3. The magnetic quantum number, m, is related to the orientation in space of an orbital within a given subshell.
Select one:
O a. 1 only
O b. 2 only
O c. 3 only
O d. 1, 2, and 3
e. Not enough information

Compare and contrast physical changes with chemical changes.

Nebulae are enormous clouds in outer space. they are made mostly of hydrogen gas, helium gas, and dust. some nebulae glow brightly, while others do not. the stars that people see are huge, bright balls of glowing gas. they are made mostly of hydrogen and helium. which statement correctly describes other ways in which nebulae and stars are different? a. stars can form inside a nebula but a nebula can never be produced by any star. b. a star always has a higher density than a nebula. c. stars can never form inside a nebula but a nebula can be produced by any star. d. a nebula always has a higher density than a star.

Explain in detail of the four major scientific developments that spurred the formulation of the plate tectonics theory