atoms, electrons and chemical bonding lecture

• Front: What is an atom defined as?

The smallest unit in which an element can exist.

What are the three subatomic particles that compose an atom, and what are their electrical charges?

Protons (positive), neutrons (neutral), and electrons (negative).

• What do the atomic number (Z) and mass number

(A) represent

atomic number (Z) = number of protons; Mass number (

(A) = sum of protons and neutrons.

• Front: The principal quantum number (n) specifies the shell and relates to the _________ of the orbital.

energy

the angular momentum quantum number (designated by letters like s,p,d,f) describes the ________ of the orbital.

shape

what shape are s orbitals and p orbitals?

(s)orbitals are spherically symmetric;

(p)orbitals are shaped like dumbbells.

A regional surface where the probability of finding an electron is zero is called a nodal__________ or node.

surface

State the Pauli Exclusion Principle regarding electrons in orbitals.

No two electrons can have the same four quantum numbers, and a maximum of two electrons with opposite spins can occupy the same orbital.

what is the octet rule

• The tendency for atoms to seek 8 electrons in their outer shells to match noble gas stability.

How are ionic bonds formed, and what types of elements are involved?

• Formed by the transfer of electrons between atoms of metals and nonmetals with very different electronegativities.

What is electronegativity?

• The measure of an atom's ability to attract electrons to itself.

Which element is the most electronegative, and which is the least?

Most electronegative = Fluorine (4.0)

Least electronegative = Francium(0.7)

• Covalent bonds are formed by the _________ of electron pairs between nonmetallic elements of similar electronegativity

sharing

a __________ Bond results when bonding orbitals point along the axis connecting the two nuclei, whereas a _________ bond results when parallel unhybridized

(p)orbitals overlap above and below the axis.

1.sigma 2.pi

true or false:(sigma) bonds are generally stronger than (pi) bonds.

true

• What is resonance?

When a molecule is represented by multiple valid structures where electrons are delocalized (shared evenly across atoms, like in ozone or benzene).

How are metal atoms held together in a metallic bond?

By a "sea of electrons" surrounding metal ions, giving high conductivity and melting points.