Chapter 5 Chem GT, Periodic Trends, Ions, Scientists

Period

Horizontal row of elements in the periodic table

Group

Vertical column of the periodic table that contains elements with similar electron configurations; also known as a family.

Metal

Element that has a high melting point, is ductile, malleable, shiny, and a good conductor of heat and electricity. 91 of the 118 known elements are metals.

Nonmetal

Element that has a low melting point and a dull surface, breaks easily, is a poor conductor of heat and electricty.

Valence Electron

Electron in the outermost energy level of an atom that can be gained or lost to form a chemical bond

Atomic Radius

Distance between the center of the nucleus of an atom and the outermost electrons

ionization energy

the energy needed to remove one of its electrons

Electron affinity

Energy change that occurs when an atom gains an electron

Electronegativity

atoms ability to attract electrons in a chemical bond

Metalloids

also known as semimetals, elements that have properties of both metals and non-metals that divide those two groups on the periodic table. Boron and silicon are examples.

malleability

the ability of a substance to be hammered or beaten into thin sheets

ductile

can be coiled into wires

How are metalloids like metals

They have luster (shine) and are semiconductive.

How are metalloids unlike metals

They are not malleable or ductile or durable

How can you determine valence electrons?

1. Write the electron configuration

2. Determine the highest energy level (1, 2, 3, etc.)

3. Count the number of electrons in that level

Lewis Dot Notations

Notation with the element symbol and surrounding dots to represent electrons

Formula for the number of electrons in any level n

2n^2

Octet Rule

8 electrons in the valence shell. Elements want to have 8 valence electrons to have full valence electron orbitals

Elements will ____ electrons to get 8 valence electrons

gain/lose electrons

Cations

Element loses electrons forming an ion with a positive charge

Anions

Element gains electrons forming an ion with a negative charge

Ways to remember cations are positive

cats are good

ca+ion

Ways to remember anions are negatives

onions, like chem tests, make you cry

An atom with more than 4 valence electrons will want to ___ and become a ___

gain electrons and become an anion

An atom with less than 4 valence electrons will want to ___ and become a ___

lose electrons and become a cation

an atom that gains x electrons is an anion denoted

[element symbol] x-

an atom that loses x electrons is a cation denoted

[element symbol] x+

What period is the border between atoms that gain electrons and those that lose electrons?

period 4

As you move down a group or family, the atomic radius gets __

larger

As you move along (left to right) on a period the atomic radius gets ___

smaller

When an atom gains electron(s) or becomes a negative ion, it ___

becomes larger. There are more electrons to repel the attractive force of the protons

When an atom loses electron(s) or becomes a positive ion, it ___

becomes smaller. There are fewer electrons to repel the attractive force of the protons

As you move down a group, ionization energies __

decrease (valence electrons are further from the nucleus so there is less pull)

As you move left to right along a period, ionization energies __

increase (atoms want to gain electrons, so they lose less readily)

As you move along a period, the electronegativity __

increases

As you move down a family, the electronegativity __

decreases

charge of an ion from period I (hydrogen, lithium, sodium)

1+

charge of an ion from period V (nitrogen, phosphorus, arsenic)

3-

charge of an ion from period II (beryllium, magnesium, calcium)

2+

charge of an ion from period VIII (helium, neon, argon)

none, as they have a full valence shell

charge of an ion from period VI (oxygen, sulfur, selenium)

2-

charge of an ion from period VII (fluorine, chlorine, bromine)

1-

charge of an ion from period III (boron, aluminium, gallium)

3+

charge of an ion from period IV (carbon, silicon, germanium)

either 4+ or 4- since they can go either way. Carbon is one of the most reactive elements.

atomic radius

the distance between the nucleus and the outermost electrons

Why does the atomic radius get larger when going down?

You are adding more shells and increasing the principal quantum number and extending electrons further from the nucleus

Why does the atomic radius get smaller when moving right?

As you move left to right, you are adding more protons which exert stronger pulls on the electrons in a given principal quantum level. This stronger attraction decreases the atomic radius.

If principal quantum number was the determining factor for atomic radius, then all of the elements along the same period would be ___

the same size

An atom's ionization energy is a reflection of __

how strongly they hold on to their outermost electrons

Atoms with high ionization energies ___ their electrons

holds on tight

Atoms with low ionization energies are more likely to __

lose one of their outermost electrons and gain a positive charge

What unit is ionization energy stated in

joules per atom

For a large collection of atoms, ionization energy is stated in

moles

First ionization energy

the energy required to remove the first electron form an isolated atom

Successive ionization energies

energies required to remove electrons beyond the first electron (second ie for second electron and so on)

Successively, it takes __ ionization energy to remove more electrons from an atom

more

It takes ___ energy to remove electrons from inner shells than from outer shells

a lot more energy (larger than the amount of energy to remove electrons from the same shell)

Eg. I1 for sodium is 496, I2 for sodium (the electron in the inner shell) if over 4000

Electronegativity applies to

atoms in a chemical bond (such as H2O)

Electronegativity is measured in

using the Pauling scale, no units

Which element has the highest electronegativity on the Pauling scale?

Fluorine

What is electronegativity useful for

Molecular bonding, polarity, reactivity

Higher electronegativity =

stronger pull on electrons

In water molecules, hydrogen electrons are ___.

Pulled towards the oxygen atom as it has a higher electronegativity

Electron affinity applies to

isolated atoms in the gas phase

Electron affinity tells us the

energy released when gaining electron(s)

an atoms attraction or affinity for an extra electron

Electron affinity is measured in

kJ/mol kilojoules per mol

Which element has the highest electron affinity

Chlorine, it has the most negative electron affinity and the largest energy release

Nonmetals have __

more negative electron affinity

Why is the electron affinity of noble gases zero?

They are full so it requires energy to add an electron

Greater attraction =

greater negative electron affinity

What did John Newlands propose?

The Octave law which arranged elements by increasing atomic mass

What did Newlands notice about elemental properties every eight elements?

They have similar properties

Who was the first person to derive a periodic table of elements

John Newlands

Who established the atomic number?

Henry Moseley

Moseley's Law

frequency = a(Z-b)^2

Z = atomic number

What does Moseley's Law explain?

the precise relationship between the characteristic X-rays emitted by an element and its atomic number

Lothar Meyer's periodic table organized elements based on

atomic weight and periodic trends and valence

Where are the alkali metals?

Group 1 (I)

Where are the alkaline earth metals?

Group 2 (II)

Where are the halogens?

Group 17 (VII)

Where are the noble gases?

Group 18 (VIII)

Law of Triads

Grouping elements into trios based on similar properties (such as lithium, sodium, and potassium). The middle element's atomic weight is the rough mean of the other two elements.

Who proposed the Law of Triads?

Johann Wolfgang Dobereiner

Dobereiner's 1st Triad

Lithium, Sodium, and Potassium

Dobereiner's 2nd Triad

Calcium, Strontium, Barium

Dobereiner's 3rd Triad

Chlorine, Bromine, Iodine

Who created the periodic table?

Dmitri Mendeleev

Periodic Law

Atoms are arranged by increasing atomic number and sorted by chemical and physical properties and groups.