What is the electron configuration of an element with atomic number 15? a. 1s2 2s2 2p6 b. 1s2 2s2 2p6 3s2 3p5 c. 1s2 2s2 2p6 3s2 3p3 d. 1s2 2s2 2p6 3s2 e. 1s2 2s2 2p6 3p3 3s2 3p1

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.