Based on the models, why do you think helium is number 2( the second element) and beryllium number 4( the fourth element) on the periodic table?

Chromosome 17 is made of over million base pairs.

Which is a characteristic of the electron sea model for metallic bonding? molecular orbitals overlap to produce bands. electrons flow easily between metal nuclei. electrons are in fixed positions in the orbitals. atomic nuclei are arranged in an irregular pattern.

Condensation happens when water vapor cools. true or false? ?