Objective 4.03

Objective 4.03: Explain how the Periodic Table is a model for:• Classifying elements• Identifying the properties of elements

Mendeleev’s Periodic Table

• Mendeleev’s periodic table arranges elements according to the atomic mass

• Atomic mass is the number of protons and neutrons

• Elements with similar properties are found in the same column

• Periodic table—chart that organizes information about all of the known elements according to their properties

http://www.aip.org/history/curie/periodic.htm

Today’s Periodic Table

• 1913, Henry Moseley showed that atomic number was the most important feature because it is what is responsible for chemical properties – Electron configuration determines chemical

properties

• Today elements are in order of the atomic number

• Atomic number—number of protons in the nucleus of an atom

Today’s Periodic Table

Periodic Table

• Chemical family or group is the Vertical column on the periodic table– All have similar properties, numbered 1-18 and

from 1A to 8A, all have same number of valence electrons

– Groups 1-2(IA-IIA) and 13-18(IIIA-VIIIA) are the main groups

– Groups 3-12 are called transition elements– Elements on the left side of the periodic table are

metals, except hydrogen– Elements on the right side of the periodic table are

nonmetals

Today’s Periodic Table

Properties of Metal Properties of NonmetalsSolid at room temperature, except mercury, which is a liquid

Most are gases, except bromine, which is a liquid

Malleable(shaped) and ductile (drawn into wire)

Brittle in solid phase

Have luster (shiny) Normally dullHave high thermal and electrical conductivity

Are poor conductors of heat and electricity

Tend to lose electrons in chemical reactions

Tend to gain electrons in chemical reactions

Reactivity describes how likely an element is to form bonds with other elements

Group 1 and Hydrogen

• Hydrogen is found above Group 1 but doesn’t belong to any group

• Placed here because it only has one valence electron. It’s properties are different from the other groups.

Alkali Metals

• Group 1 (Alkali Metals) on periodic table– Most chemically active – One electron in the

outer shell– Easily combine with

nonmetals– Reactivity of the metal

decreases with increasing atomic number

Reac

tivity

incr

ease

s

Alkaline Earth Metals

• Group 2 (Alkaline Earth Metal) on the periodic table – Highly reactive but less

reactive than group 1– Reactivity of the metal

increases with increasing atomic number

Reac

tivity

incr

ease

s

Transition Metals

• Group 3 –12 (transition metals) on the periodic table– Generally hard solids

with high melting points – Often form colored ions

Metalloids

• Metalloids– Found along the zigzag

between the metals and nonmetals on the periodic table

– Have properties of both metals and nonmetals

http://www.gordonengland.co.uk/elements/metaloids.htm

Halogens

• Group 17 (Halogens) on the periodic table– Most reactive of the nonmetals– Reactivity in nonmetals

increases as atomic number decreases

– Fluorine (F) is the most reactive

– Halogens react with alkali metals to form salts

– Elements in this family are all states of matter• Fluorine(Fl) and Chlorine—

gases• Bromine (Br)—liquid • Iodine (I) and Astatine (At) are

solids at room temperature

Noble Gases

• Group 18 (Noble Gases) on periodic table– Least reactive of all

elements– Inert—unable to react

chemically

Periods

• Periods are the rows• Elements in the same

period have the same number of electron orbits(shells)

• Atoms are similar sizes

• Electronegativity (tendency to attract electrons) increases from left to righthttp://www.chem4kids.com/files/elem_pertable.html

Periodic Table

• http://www.periodictable.com/

• http://www.bbc.co.uk/schools/ks3bitesize/science/chemical_material_behaviour/particle_model/revise1.shtml