chem unit 2

Horizontal row in periodic table

Horizontal row in periodic table

Period

Vertical column in periodic table

Group

A repetition of properties occurs when elements are arranged in order of increasing atomic number

Periodic law

Type of element that is a good conductor of heat and electric current

Metal

Type of element characterized by the presence of electrons in the d orbital

Transition metal

One-half the distance between the nuclei of two atoms when the atoms are joined

Atomic radius

Type of ion formed by Group 2A elements

Cation

Subatomic particles that are transferred to form positive and negative ions

Electrons

Ability of an atom to attract electrons when the atom is in a compound

Electronegatvity

Energy required to remove an electron from an atom

Ionization energy

How does atomic radius change from top to bottom in a group in the periodic table?

It tends to increase.

How does atomic radius change from left to right across a period in the periodic table?

It tends to decrease.

What causes the shielding effect to remain constant across a period?

Electrons are added to the same principal energy level.

What element in the second period has the largest atomic radius?

Lithium

What is the element with the lowest electronegativity value?

Cesium

What is the element with the highest electronegativity value?

fluorine

What is the energy required to remove an electron from an atom in the gaseous state called?

ionization energy

Electronegativity generally increases

from left to right across a period.

Compared with the electronegativities of the elements on the left side of a period, the electronegativities of the elements on the right side of the same period tend to be

higher

Which of the following decreases with increasing atomic number in Group 2?

ionization energy

Which of these describes a tendency for atomic radii as displayed on the periodic chart?

Atomic radii decrease left to right across  a period.

Which scientist first arranged elements by atomic number?

Mosely

Which category of elements have the property of being malleable and ductile?

Metals

4 types of sublevels

S P D F

Inside a sublevel

Orbitals

Orbitals

3d spaces and can hold a max of two electrons

Inside the orbitals

Electrons

S level

1 orbital with 2 electrons

P level

3 orbitals with 6 electrons

D level

5 orbitals with 10 electrons

The periodic table has

7 energy levels, each level has 4 sublevels (S,P,D,F), and each sublevel has a/an orbital

Electrons will go to

least energy possible (usually)

Aufbau Principle

electrons always occupy the lowest available energy level

Exceptions to the Aufbau Principle

An electron configuration cannot end in d4 or d9

Pauli Exclusion Principle

Two electrons may occupy a single orbital, but they must spin in opposite directions

Hund’s Rule

orbitals of equal energy will half-fill before the electrons will pair up

Noble Gases

completely filled outer energy level (Group 18)

Valence Electrons

electrons located on the highest energy level

◼ only located in the s and p blocks

◼ d and f blocks only contain 2 valence e-

◼ the number of valence e- corresponds to the group number for s and p (#1 has 1, #2 has 2, #13 has 3, …)

◼ the maximum # of valence e- is 8

Core Electrons

all other electrons excluding the valence electrons (electrons that are closest to the nucleus)

Ion

an atom with an overall negative or positive charge (electrons have been added or removed)

Cation

an atom with an overall negative or positive charge (electrons have been added or removed)

Cation

– positively charged ion

Anion

negatively charged ion

Ion and elements having same number of electrons are called

isoelectronic

Periodic Table - History

Developed independently by German Julius Lothar Meyer and Russian Dmitri Mendeleev (1870’s)

• Put in columns by similar properties

• Predicted properties of missing elements

• Left spaces for yet undiscovered elements

• Elements in order of increasing atomic mass

Effective Nuclear Charge (Zeff)

the net positive charge experienced by valence electrons, approximated by the equation: Zeff = Z – S, where Z is the atomic number and S is the number of shielding electrons …basically the strength of the attraction a valence electron feels toward the nucleus

Atomic Radius Trend WITHIN A GROUP

general increase in size as you move down a group

◼ Size increases due to additional energy levels—increasing distance from the nucleus

◼ valence electrons ARE shielded from increasing pull from the nucleus (effective nuclear charge) by increasing number of core electrons

Atomic Radius Trend WITHIN A PERIOD

general decrease in atomic radius moving from left to right across a period

◼ increasing protons in the nucleus and the fact that the principal energy level stays the same

◼ additional electrons are pulled closer into the nucleus as you move left to right across a period

Ionization energy:

the energy needed to remove an electron from an atom

Ionization energy Trend within a group (top to bottom):

additional energy levels

◼ distance between the nucleus and valence electrons is becoming greater

◼ weaker effective nuclear charge

◼ less energy is required to remove electrons ◼ general decrease in ionization energies

Ionization energy Trend within a period (left to right)

same energy level with additional protons

◼ stronger effective nuclear charge

◼ increased hold on the valence electrons

◼ general increase in ionization energies

First ionization energy (I1 ) is

that required to remove the first electron

Second ionization energy (I2 ) -

To remove the second electron

Increasing energy required

to remove successive electrons…Zeff → I1 < I2 < I3 …

Electron Affinity

The energy change associated with the addition of an electron to a gaseous atom. X(g) + e− → X− (g)

When the addition of an electron makes the atom more stable,

energy is given off (exothermic)

When the addition of an electron makes the atom less stable,

energy must be put in (endothermic)

…thus metals tend to have positive electron affinities while

nonmetals tend to have negative electron affinities

Electronegativity

tendency for an atom to attract electrons to itself when it is bonded to another atom

Noble gases rarely form compounds, so

they are not given electronegativity values

Electronegativity Trend within a group (top to bottom):

Increasing number of filled energy levels

◼ Weaker effective nuclear charge

◼ Electronegativity decreases

Electronegativity Trend within a period (left to right):

Same number of energy levels

◼ Increasing number of protons

◼ Stronger effective nuclear charge

◼ Electronegativity increases

If electrons are held more strongly,

it will equire more energy to remove successive electrons

Farther out an electron is

force of attraction weaker

If the force of attraction increases between proton and electron

Atomic radius decreases

The attraction between protons and electrons decrease the distance making the size

smaller

If the force of attraction decreases between protons and electrons

atomic radius (size) increases

Shielding

Increases size. Core electrons shield valence electrons from protons.

Force of attraction becomes stronger because

adding electrons in the same energy level