Which of the following is a physical change: a. turning solid sodium to and chlorine gas to salt
b. forming a mixture
c. food turning into waste in the intestines
d. burning wood

This is easy the answer is b forming a mixture your welcome hope this helps and good luck

If a hydrogen atom is neutral, it must also have  one electron. an oxygen atom (o) has an atomic number of eight (8). this means a neutral oxygen atom has eight protons and eight electrons. the element actium (ac) has an atomic number of 89, so it has 89 protons and 89 electrons in a neutral atom