Chapter 15 – Elements & The Periodic Table

15.1 The Periodic Table of the Elements– (pp. 334-340)

Periodic Table Timeline

Lavoisier (1770-1789) Composed the first list of 33 elements. Distinguished metals from nonmetals.

Berzelius (1828) Created a table of atomic weights. Introduced idea of chemical symbols.

Dobereiner (1829) Developed triads-groups of 3 elements with similar properties.

Newlands (1864) Arranged known elements in order of increasing atomic weights. Proposed the Law of Octaves.

Meyer (1869) Compiled a periodic table with elements arranged by atomic weight. Elements with similar properties arranged in columns.

Mendeleev (1869) Created a periodic with elements arranged by atomic weight. Elements with similar properties arranged in columns.

Ramsay (1894) Discovered noble gases.

Moseley (1914) Determined atomic numbers of each element. Modified the periodic law-an element’s properties varies periodically with its atomic numbers.

Seaborg (1940) Synthesized elements beyond uranium.

15.1 Physical properties

Characteristics that you can see through direct observation are called physical properties.

Physical properties include color, texture, density, brittleness, and state (solid, liquid, or gas).

Melting point, boiling point, and specific heat are also physical properties.

15.1 Physical properties

A physical change does not result in a new substance being formed.

15.1 Chemical propertiesProperties that can only be observed

when one substance changes into a different substance are called chemical properties.

Any change that transforms one substance into a different substance is called a chemical change.

15.1 The Periodic Table

The periodic table organizes the elements according to how they combine with other elements (chemical properties).

The periodic table is organized in order of increasing atomic number.

15.1 The Periodic Table

The periodic table is further divided into periods and groups.

Each horizontal row is called a period.

Each vertical column is called a group or family.

15.1 Atomic Number Remember, the atomic number is the number of

protons all atoms of that element have in their nuclei. This number does not change for that element.

If the atom is neutral, it will have the same number of electrons as protons.

15.1 Atomic Mass The mass of individual atoms is so small

that the numbers are difficult to work with. To make calculations easier, scientists use

the atomic mass unit (amu). The atomic mass of any element is the

average mass (in amu) of an atom of each element.

15.1 Atomic Mass Atomic masses differ

from mass numbers because most elements in nature contain more than one isotope.

15.1 The Periodic Table All the elements in Group

1 of the periodic table form similar compounds.

The metals lithium, sodium, and potassium all form compounds with a ratio of 2 atoms of the metal to 1 atom of oxygen.

GROUPS 1 & 2VERY REACTIVE METALSGroup 1 – The Alkali Metals

The most reactive metals1 electron in outer energy levelOther shared properties – soft, silver colored; shiny; low

density

Group 2 – The Alkaline Earth Metals-very reactive, but less reactive than alkali metals

2 electrons in outer energy levelOther shared properties – silver colored; more dense than

alkali metals

THE TRANSITION METALS

Groups 3-12 1 or 2 electrons in outer energy level Less reactive than alkaline earth metals Lanthanides and actinides are included in this

group Other shared properties: shiny; good

conductors of thermal energy and electric current; higher densities and melting points than elements in Groups 1 & 2

LANTHANIDES

They follow the element Lanthanum.

Shiny, reactive metals

ACTINIDES

They follow the element Actinium All are radioactive. This means they are

unstable. Elements listed after Plutonium (element

94) do not occur in nature. They are man made.

GROUP 13

Also known as the Boron Group 3 electrons in the outer energy level Group contains Boron (a metalloid) and 4 metals

(Al - aluminum, Ga - gallium, In - indium & Tl- thallium)

Reactive Other shared properties: solid at room

temperature

GROUP 14

Also known as the Carbon Group 4 electrons in outer energy level Reactivity varies among the elements Group contains 1 nonmetal (carbon), 2

metalloids (Si - silicon & Ge - Germanium) and 3 metals (Sn - tin, Pb - lead and Uuq)

Other shared properties: solid at room temperature

GROUP 15

Also known as the Nitrogen Group Have 5 electrons in the outer energy level Reactivity varies among the elements Group contains 2 nonmetals (N - nitrogen & P -

phosphorus), 2 metalloids (As- Arsenic & Sb - antimony) & 1 metal (Bi - bismuth)

Other shared properties: all but Nitrogen are solid at room temperature

GROUP 16

Also known as the Oxygen Group Have 6 electrons in the outer energy level Very reactive Contains 3 nonmetals (O - oxygen, S - sulfur &

Se - selenium), 1 metalloid (Te - tellurium) & 2 metals (Po - polonium & Uuh)

Other shared properties: all but Oxygen are solid at room temperature

GROUP 17

Also known as the Halogens Group contains all nonmetals (F - fluorine, Cl -

chlorine, Br - bromine, I – iodine & At - astatine) Very reactive There are 7 electrons in the outer energy level Other shared properties: poor conductors of

electric current; react violently with alkali metals to form salts; never found uncombined in nature.

GROUP 18

Also known as the Noble Gases Group contains all nonmetals (He - helium, Ne -

neon, Ar - argon, Kr - krypton, Xe - xenon, Rn – radon & Uuo)

There are 8 electrons in the outer energy level (He only has 2)

They are unreactive. Other shared properties: colorless, odorless

gases at room temperature

HYDROGEN

Stands apart Only 1 electron in the outer energy level Very reactive Other properties: colorless, odorless gas

at room temperature; low density; reacts explosively with oxygen.