Elements, Atoms, and

Ions

Chemistry I: Chapter 2b

Chemistry I Honors: Chapter 3

ICP: Chapter 17

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The Language of The Language of ChemistryChemistryThe Language of The Language of ChemistryChemistry

• CHEMICAL ELEMENTSCHEMICAL ELEMENTS - - – pure substances that cannot be decomposed by pure substances that cannot be decomposed by

ordinary means to other substances.ordinary means to other substances.

SodiumBromine

Aluminum

The Language of The Language of ChemistryChemistryThe Language of The Language of ChemistryChemistry

• The elements, The elements, their names, and their names, and symbols are given symbols are given on theon the PERIODIC PERIODIC TABLETABLE

• How many How many elements are elements are there?there?

The Periodic TableThe Periodic Table

Dmitri Mendeleev (1834 - 1907)Dmitri Mendeleev (1834 - 1907)

Glenn Glenn SeaborgSeaborg

(1912-1999 )(1912-1999 )• Discovered 8 Discovered 8

new elements.new elements.

• Only living Only living person for person for whom an whom an element was element was named.named.

An atom consists of aAn atom consists of a

• nucleusnucleus

– (of (of protonsprotons and and neutronsneutrons) )

• electronselectrons in space about the nucleus. in space about the nucleus.

The The AtomAtom

NucleusNucleus

Electron cloudElectron cloud

Copper Copper atoms on atoms on silica silica surface.surface.

• An An __________ is the smallest particle of is the smallest particle of an element that has the chemical an element that has the chemical properties of the element.properties of the element.

Distance across = 1.8 nanometer (1.8 x 10-9 m)

ATOM ATOM COMPOSITIONCOMPOSITION

•protons and neutrons in protons and neutrons in the nucleus.the nucleus.

•the number of electrons is equal to the the number of electrons is equal to the number of protons.number of protons.

•electrons in space around the nucleus.electrons in space around the nucleus.

•extremely small. One teaspoon of water has extremely small. One teaspoon of water has 3 times as many atoms as the Atlantic Ocean 3 times as many atoms as the Atlantic Ocean has teaspoons of water.has teaspoons of water.

The atom is mostlyThe atom is mostlyempty spaceempty space

ATOMIC COMPOSITIONATOMIC COMPOSITION• Protons (pProtons (p++))

– + electrical charge+ electrical charge

– mass = 1.672623 x 10mass = 1.672623 x 10-24-24 g g

– relative mass = 1.007 atomic relative mass = 1.007 atomic mass units mass units (amu) (amu) but we can round to 1but we can round to 1

• Electrons (eElectrons (e--))– negative electrical chargenegative electrical charge

– relative mass = 0.0005 amu relative mass = 0.0005 amu but we can round to 0but we can round to 0

• Neutrons (nNeutrons (noo))– no electrical chargeno electrical charge

– mass = 1.009 amu mass = 1.009 amu but we can round to 1but we can round to 1

Atomic Number, ZAtomic Number, Z

All atoms of the same element All atoms of the same element have the same number of have the same number of protons in the nucleus, protons in the nucleus, ZZ

1313

AlAl

26.98126.981

Atomic numberAtomic number

Atom symbolAtom symbol

AVERAGE Atomic MassAVERAGE Atomic Mass

Mass Number, AMass Number, A• C atom with 6 protons and 6 neutrons C atom with 6 protons and 6 neutrons

is the mass standard is the mass standard • = 12 atomic mass units= 12 atomic mass units• Mass NumberMass Number (A) (A)

= # protons + # neutrons= # protons + # neutrons• NOT on the periodic table…(it is the NOT on the periodic table…(it is the

AVERAGE atomic mass on the table)AVERAGE atomic mass on the table)• A boron atom can have A boron atom can have

A = 5 p + 5 n = 10 amuA = 5 p + 5 n = 10 amu

A

Z

10

5B

A

Z

10

5B

Counting Protons, Neutrons, and Electrons

• Protons: Atomic Number (from periodic table)• Neutrons: Mass Number minus the number of protons

(mass number is protons and neutrons because the mass of electrons is negligible)

• Electrons: – If it’s an atom, the protons and electrons must be

the SAME so that it is has a net charge of zero (equal numbers of + and -)

– If it does NOT have an equal number of electrons, it is not an atom, it is an ION. For each negative charge, add an extra electron. For each positive charge, subtract an electron (Don’t add a proton!!! That changes the element!)

Learning Check – Counting

Naturally occurring carbon consists of three isotopes, 12C, 13C, and 14C. State the number of protons, neutrons, and electrons in each of these carbon atoms.

12C 13C 14C 6 6 6

#p+ _______ _______ _______

#no _______ _______ _______

#e- _______ _______ _______

Answers

12C 13C 14C 6 6 6

#p+ 6 6 6

#no 6 7 8

#e- 6 6 6

PeriodsPeriods in the Periodic in the Periodic TableTable