Periodic Table

• Why is the periodic table so important?• Why is the periodic

table shaped the way it is?• Why do elements

combine?• Why do they react?• What other patterns are

there in the world and how do they help us?

• John Newland arranged elements according to their chemical and physical properties. He noticed the pattern repeated every eight elements, so he called it the law of octaves.

• Moseley showed that elements are arranged by their atomic number, not their atomic mass.

•Dmitri Mendeleev invented to first periodic table in 1869. He arranged the 63 elements that were known during his time. He came up with symbols for each element.

•Two important observations came from his table: one he left gaps, where he assumed missing elements were, and two he noticed elements don’t always fit in order of atomic mass.

• Periodic Law – the law that states that the repeating physical and chemical properties of elements change periodically with their atomic number

• Valence Electrons – an electron that is found in the outermost shell of an atom and that determines the atom’s chemical properties.

• Group- a vertical column of elements in the periodic table; elements in a group share chemical properties

• Period – a horizontal row of elements in the periodic table

• KEY IDEAS • John Newlands, Dmitri Mendeleev,

and Henry Moseley contributed to the development of the periodic table.

• The periodic law states that the properties of elements are periodic functions of the elements’ atomic numbers.

• In the periodic table, elements are ordered by increasing atomic number. Rows are called periods. Columns are called groups.

• Elements in the same period have the same number of occupied energy levels. Elements in the same group have the same number of valence electrons.

Four elements – hydrogen, oxygen, carbon, and nitrogen – account for more than 99% of all atoms in the human body.

• Main group elements are in the s-block or p-block of the periodic table.

• Main-group elements have diverse properties and uses. They are highlighted in the groups on the left of right sides of the periodic table.

• Alkali metals- one of the elements of Group 1 of the periodic table (lithium, sodium, potassium, rubidium, cesium, and francium)

• They are very reactive because they only have one valence electron.

• Because they are so reactive they are stored in oil, and never found as a pure substance in nature, because they would react with oxygen and water in the air.

• They combine with other elements to form compounds.

• All of these elements are so soft they can be cut with a knife; at first is shiny, then becomes dull because of the air; good conductors of electricity.

• Alkaline-Earth Metals are less reactive than Alkali Metals. Include all Group 2 elements.

• -Silvered colored, soft metals, which react readily with halogens to form ionic salts.

Halogens

*Very Reactive

*Group 17

*Nonmetals

*This is the only group of elements that can be found as a solid, liquid, or a gas.

• Noble Gases are found in Group 18. Normally these elements are all odorless, colorless, and has a very low chemical reactivity. Six noble gases are found naturally: He, Ne, Ar, Kr, Xe, and Rn. Their outer shell of valence electrons are considered to be full; therefore, they don’t react with other elements very often.

• Hydrogen- A class all of it’s own.

• colorless, odorless, nonmetallic, tasteless, and highly flammable when represented as H2

• Most abundant element

• Stars consist of hydrogen

• In ionic compounds, it can take a positive or negative charge

Metals share many of the same properties. Excellent conductors of electricityCan be very brittleDuctile – can be squeezed into wireMalleable – can be rolled into thin

sheets

The regions highlights in blue indicate the elements that are metals.

• Transition metals occupy the center of the Periodic Table• Groups 3-12• Not as reactive as other

groups• Sometimes don’t form

compounds because they don’t react.

• Lanthanides are the elements 58-71

• Actinides are elements 89-103• Lanthanides are used to produce

color T.V. screens• Actinides are ALL radioactive

• Metals usually mix with other metals to form an alloy. • They mix metals to get the

best at of the two individual metals, one example is brass. A mix of copper and zinc. Brass has a wide range of uses.

• The main-group elements are Group 1, Group 2, Groups 13-16, Group 17, and Group 18.• Hydrogen is in a class all

of it’s own.• Most elements are

metals, which conduct electricity.

• Ionization energy is the energy required to remove an electron from an atom or ion

• Ionization energy decreases as you move down a group

• Electron shielding is the reduction of the attractive force between a positively charged nucleus and its outermost electrons due to the cancellation of some of the positive charge by the negative charges of the inner electrons

Ionization Energy

Atomic radius increases as you move down a group.

• Electronegativity is a measure of the ability of an atom in a chemical compound to attract electrons.

• Electronegativity decreases as you move down a group.

• Ionic size tends to increase down groups and decrease across periods. • Electron affinity

generally decreases down a group and increases across periods.

• Periodic trends are related to the atomic structure of the elements.

• Ionization energy, electronegativity, and electron affinity generally increase as you move across a period and decrease as you move down a group.

• Atomic radius and ionic size generally decrease as you move across a period and increase as you move down a group.

• Melting points and boiling points pass through two cycles of increasing, peaking, and then decreasing as you move across a period.

•Hydrogen and Helium formed after the Big Bang. •A nuclear reaction is a

reaction that affects the nucleus of an atom.• Stars are formed from

this process.

• Transmutations are a type of nuclear reaction. It changes the nucleus of an atom and therefore cannot be achieved by ordinary chemical means.

• Synthetic elements are made by using a special piece of equipment called a particle accelerator.

• The 93 natural elements were formed in the interiors of stars. Synthetic elements are made using particle accelerators.• A transmutation is a

nuclear reaction in which one nucleus is changed into another nucleus.

• Used Chemistry book written by Myers, Oldham, and Tocci. Information from chapter four.