Sodium has one electron in its outermost energy level. To reach a stable energy configuration, sodium will tend to____.​

The most exclusive and smallest grouping in the classification of living organisms is the ____.​

The substance H2O is considered to be ____.​

Which of the three sub-atomic particles are charged?​

A pure substance that cannot be broken down into simpler substances by ordinary chemical or physical techniques.  

Which element is likely to be chemically unreactive?​

The smallest unit that retains the chemical and physical properties of an element is a(n) ____.​

The substance O2 is considered to be ____.​

Isotopes of the same element differ from each other in the number of ____.​

All the populations of different organisms that live in the same place form a(n) ____.​