- Calvin Coolidge (Wikipedia)
Calvin Coolidge (born John Calvin Coolidge Jr.; /ˈkuːlɪdʒ/; July 4, 1872 – January 5, 1933) was an American attorney and politician who served as the 30th president of the United States from 1923 to 1929.
- Covalent bond (Wikipedia)
A covalent bond is a chemical bond that involves the sharing of electrons to form electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs. The stable balance of attractive and repulsive forces between atoms, when they share electrons, is known as covalent bonding. For many molecules, the sharing of electrons allows each atom to attain the equivalent of a full valence shell, corresponding to a stable electronic configuration. In organic chemistry, covalent bonding is much more common than ionic bonding, where atoms are separate and merely associated by electrostatic attraction.