The numbers listed represent the first, second and third energy levels, respectively. On this basis, which of the following is an unstable or reactive atom?

Mis amigos y yo ___________________ ____ la universidad. (Aprender a/ Asistir a)

PCV stands for 

Proteins are formed by ______ different amino acids.

Metabolism is the sum of

When two atoms are held together because their valence electrons are attracted by opposite charges, they are united by

Mis abuelos paternos no ___________ de este país.

Tú ______________________ una bicicleta, ¿verdad?  

Mujer de Guatemala

Calcium homeostasis in adults is maintained mainly by