Which of these are isotopes of hydrogen?

Which of the following elements is most similar to chlorine?

How many protons, electrons, and neutrons, respectively, does have?

How many electrons are present in a bromine atom with a mass number of 87?

The total number of oxygen atoms indicated by the formula Ti3(PO4)2 is

How many protons, electrons, and neutrons, respectively, does 81Br have?

How many atoms of hydrogen are in three molecules of C4H9Cl?

How many protons are in the atom ?

H2 is a/an

The electron configuration for an atom is 1s2 2s2 2p3.  The atomic number of the element is