Chem Chapter 6 Williams

Periodic Trends

Mendeleev

Mendeleev

During the 19th century, information was being published about many different compounds which needed to be organized. Mendeleev’s (periodic) table was the first to gain wide acceptance. he identified “blanks” in the table.These blanks were the predictions of yet undiscovered elements

what is most of earth's surface made up of?

Silicon Dioxide

what is earth's core made up of?

Iron and nickel

what is plutonium used for?

thermonuclear bombs

bottom two rows of periodic table

separated to fit on textbook page. f orbitals. result of the manhattan project.

Basic organization of the periodic table

Increasing atomic number, Metals, metalloids and nonmetals (metals conduct, are shiny), Groups (vertical columns), Periods (horizontal rows)

element families

Group 1: Alkali metals. Group 2: alkali earth metals. Groups 3 - 12: Transition metals. Group 17: Halogens. Group 18: Noble Gasses. Lanthanide series and Actinide series

noble gas

gas with full energy levels (stable)

trends within a group

Electron configurations within a group follows a pattern

atomic radius

Increase moving down within a group. Down a group, the number of energy levels (n) increases, so there is a greater distance between the nucleus and the outermost orbital. This results in a larger atomic radius. Decrease across a period. Within a period, protons are added to the nucleus as electrons are being added to the same principal energy level. These electrons are gradually pulled closer to the nucleus because of its increased positive charge. Since the force of attraction between nuclei and electrons increases, the size of the atoms decrease

why are there some small spikes of atomic radius along the period?

There are some small spikes in the D orbitals because of Hund’s rule: when the electrons jump to the D orbital, it stabilizes the energy, which increases the atomic diameter

overall trend atomic radius vs atomic number

increase, then trends eventually flatten out because the energy levels are getting closer together

Ionization energy

the energy needed to remove an electron from an atom is called the ionization energy. ions are formed when an atom gains or loses 1 or more electrons

cation

atom has lost 1 or more electrons

anion

atom has gained one or more electrons

factors in ionization energy

electron - electron repulsion (it is harder to move an electron when there is no repulsion force), it is harder to remove an electron from a full valence shell. the closer the electron is to the nucleus the harder it is to remove.

Trends for first ionization energy

First ionization energy generally decreases as you move down a group. This is because the outermost electron is, on average, farther from the nucleus, meaning it is held less tightly and requires less energy to remove. First ionization energy generally increases as you move left to right across a period. This is due to increasing nuclear charge, which results in the outermost electron being more strongly bound to the nucleus

Ionic Radius

the radius of a cation or anion. Atomic radius increases in a group and decreases going across the periodic table. Ionic radius increases in a group and decreases across the periodic table. When moving across a period, the ionic radius decreases until the metalloids then the anions form so it gets bigger then decreases again. It tries to get to the noble gas configuration. It will form cations or anions based on how close it is to each side. If it is easier to lose the electron it will form a cation. If it is easier to gain an electron it will form an anion.

electronegativity

Electronegativity: The desire to acquire an electron. Fluorine is the reference point “4.0”. Group: electronegativity decreases because there is an increased distance to the nucleus. Period: When moving left to right the electronegativity increases because the charge of the nucleus gets stronger so it attracts the electrons more

electrical force

F = K (e-•pt)/r2

shielding effect

When two electrons are being repulsed by each other, there is less electronegativity

Electronegativity vs electron affinity

Electronegativity refers to the ability of the atoms to attract electrons from the other elements. Electron affinity refers to the amount of energy that is liberated whenever a molecule or a neutral atom tends to acquire an electron from the other elements. It is applied only to a single atom.