How Atoms Combine

Find valence electrons. Check how many electrons are needed for a stable outer shell. Decide whether transfer or sharing is more suitable. Write the resulting bond type.

Bohr shell diagrams can show valence electrons before and after combination.

Writing that atoms combine only to increase mass is wrong because chemical combination depends mainly on electron arrangement and stability.

Atoms combine with other atoms by losing, gaining, or sharing electrons so that they can become more stable.

Atoms combine with other atoms by losing, gaining, or sharing electrons so that they can become more stable. Atoms generally combine to achieve stable outer-shell arrangements through electron transfer or electron sharing. Sodium loses one electron and chlorine gains one electron to form sodium chloride, while two hydrogen atoms share electrons with oxygen to form water.

The outermost shell of an atom controls its combining behaviour. Atoms with incomplete outer shells tend to combine in a way that gives them a stable electronic arrangement, often similar to noble gases. Atoms generally combine to achieve stable outer-shell arrangements through electron transfer or electron sharing. A chlorine atom has seven valence electrons. It can gain one electron from sodium to complete its outer shell and form chloride ion. Asked as a reason why atoms form bonds, or to identify whether a given case shows transfer or sharing of electrons. Writing that atoms combine only to increase mass is wrong because chemical combination depends mainly on electron arrangement and stability.