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True-False Quiz 9 - Atoms, Molecules, and Chemical Bonds:
True / False

The simplest atom of all is hydrogen which has 1 proton and 1 neutron in the nucleus.

Hydrogen has only 1 electron in the first shell although it could hold 2 electrons.

Isotopes are atoms with the same number of neutrons but different numbers of protons.

When an atom loses electrons it becomes a positive ion or cation. When an atom gains electrons it becomes a negative ion or anion.

Most biologically important atoms can hold 8 electrons in their outermost shell.
True / False

Carbon has an atomic # of 12 so it has 6 valence electrons.

Atoms can only form chemical bonds by either gaining or losing electrons.

Since oxygen has a valence of 6 it only needs to gain 2 more electrons to be stable.

All of these substances possess covalent bonds: CH4, CO2, NaCl, H2O

Sodium (metal) and chlorine (non-metal) form ions and an ionic bond holds them together.
True / False

Electrons are shared unequally in a polar covalent bond.

In the molecule H-H the single bond is polar covalent.

In the molecule H-Br the H would have a partial negative charge and the Br would have a partial positive charge.

Unlike Bohr diagrams, Lewis (dot) diagrams show all the electrons of an atom.

The bond C-H is polar covalent because it's between 2 different atoms. But a molecule if CH4 is symmetrical and therefore non-polar overall.
True / False

A hydrogen bond is stronger than either an ionic or a covalent bond.

Hydrogen bonds commonly form between hydrogen and an oxygen (H---O) or nitrogen (ie. H---N) on a separate molecule.

For the molecule O=O there is a total of 4 electrons in the shared double bond.

The carbon atom typically makes 4 bonds to other atoms.

Because CO2 is a bent (not linear) molecule it is non-polar overall.