The electron configuration of an element is 1s22s2. How many valence electrons does the element have?

Consider the two electron arrangements for neutral atoms a and b. are atoms a and b the same element? a - 1s2, 2s2, 2p6, 3s1 b - 1s2, 2s2, 2p6, 5s1

The tilt of the earth's axis of rotation is responsible for the a) ocean's tides. b) size of the moon. c) brightness of stars. d) earth’s seasons.

Which of the following shapes would represent a molecule with two bonded atoms and 3 lone pairs on only one of them , trigonal planar , bent , trigonal pyramidal , linear