CHM 1020 Lesson 1-4

The principal quantum number

symbolized by n, indicates the main energy level occupied by the electron

electron configuration

the arrangement of electrons in the orbitals of an atom

Shielding

the effect on an electron of repulsion by electrons in lower-energy orbitals that screen it from the full effects of nuclear charge

electron affinity

the energy change for the process of adding an electron to a gaseous atom to form an anion (negative ion). EA1: X(g)+e−⟶X−(g)

Aufbau Principle

the rule that electrons occupy the orbitals of lowest energy first

The most common ion of sulfur has what charge? A. -2 B. -1 C. +1 D. +2

A

valance shell

outermost electron shell

The horizontal rows on the periodic table are called ________.

periods

Based on the periodic trends, which atom below is least likely to form a cation? A. Sulfur (S) B. Chlorine (Cl) C. Aluminum (Al) D. Sodium (Na)

B

A column on the periodic table

Displays elements that are similar in their chemical properties due to having a similar arrangement of outer shell electrons

Sorting Atomic Radii EXAMPLE: Predict the order of increasing covalent radius for Ge, Fl, Br, Kr. Solution Radius increases as we move down a group, so Ge < Fl (Note: Fl is the symbol for flerovium, element 114, NOT fluorine). Radius decreases as we move across a period, so Kr < Br < Ge. Putting the trends together, we obtain Kr < Br < Ge < Fl. Check Your Learning Give an example of an atom whose size is smaller than fluorine.

ANSWER: Ne or He

What element is found in group 4A, period 3?

Si

octet rule

States that atoms lose, gain or share electrons in order to acquire a full set of eight valence electrons

ionization energy

The amount of energy required to remove an electron from an atom Ionization energy increases when going right on a period Ionization energy decreases when going down a group

Pauli's Exclusion Principle

When two electrons occupy the same orbital, they must have opposite spins, so we represent them as one up arrow and one down arrow

The atomic number (Z)

Z refers to the atomic number. The atomic number represents the number of protons in an atom.

Chlorine is much more likely to exist as a negative ion than sodium. This is because: A. sodium is a larger atom than chlorine B. chlorine has a greater electronegativity than sodium C. sodium is a solid and chlorine is a gas D. chlorine has a greater ionization energy than sodium

b

The periodic table is organized by increasing atomic number. Elements within the same_________have similar physical and chemical properties.

column

atomic radius

one-half the distance between the nuclei of identical atoms that are bonded together

Hund's rule

electrons will only pair up in an orbital if there are no empty orbitals left in that subshell.

The periodic table is organized by increasing atomic number. Elements within the same ________ have similar physical and chemical properties.

group

The vertical columns on the periodic table are called _________.

groups

covalent radius

one-half the distance between the nuclei of two identical atoms when they are joined by a covalent bond (this measurement is possible because atoms within molecules still retain much of their atomic identity)

The first ionization energies of the elements __________ as you go from left to right across a period of the periodic table, and __________ as you go from the bottom to the top of a group in the table.

increase. increase

IONIC RADII

measured distance from the center of an ion to its outer electrons A cation always has fewer electrons and the same number of protons as the parent atom; it is smaller than the atom from which it is derived

Boron (B), silicon (Si), antimony (Sb) and tellurium (Te) are all what type of element?

metalliods