All of the following increase from left to right across the second period of the periodic table (na - ar) except

effective nuclear charge
number of core electrons
number of valence electrons
atomic number

The climate of the continental united states is generally 1. tropical 2. temperate 3. arctic 4. highland

Compare and contrast physical changes with chemical changes.

Ants live on acacia trees in south america. the ants feed on sugars secreted by the trees. the trees provide room for the ants to live. the ants sting any other insect or animal that comes to eat the trees. what type of relationship is this?