An atom is the smallest particle of an element that retains the chemical identity of the element....

An atom is the smallest particle of an element that retains the chemical identity of the element.

Three Parts of Atom

Particle Charge Mass Atomic mass unitsProton +1 1.67x 10-24 g 1 amuNeutron 0 1.67x 10-24 g 1 amuElectron -1 9.11x 10-28 g 0 amu

Where are they?

• Nucleus is made up of protons and neutrons.• Electrons move around the nucleus.• Mass is concentrated in the nucleus.• 99.97% of the mass is in the nucleus.

How big are atoms?

• If nucleus is size of a golf ball, the electrons are how far away?

• 1 mile! Lots of empty space• How big are they?• 6.02 x 1023 atoms in 12 grams of carbon.

How many protons?

• The atomic number is the number of protons in the nucleus of the atom.

Look at the periodic table for this.

The number of protons identifies the element.

How many neutrons?

• The number of neutrons may vary.• An isotope is an atom that has the same number of

protons as other atoms of the same element, but different number of neutrons.

• Same atomic number = same element• Protons + Neutrons = Atomic Mass• Isotopes have different atomic masses, because they

have different number of neutrons.

HOW MUCH FOR A ROOT BEER?

A NEUTRON WALKED INTO A BAR AND ASKED…

FOR YOU, BUDDY…

NO CHARGE!

THE BARTENDER SAID

How many electrons?

• The number of electrons equals the number of protons in a neutral atom

• An ion is a charged atom in which the number of electrons can increase or decrease.

• More electrons than protons, charge is negative

• Fewer electrons than protons, charge is positive

CARBON

Carbon has • 6 protons 6 amu• 6 neutrons 6 amu• 6 electrons 0 amu

• Total atomic mass = 12 amu

How do we write this?• Carbon-12• C-12• 12C• 12 6 C0

• The periodic table tells us that carbon has 6 protons.• The mass is 12 amu and equals protons plus

neutrons, so it has 6 neutrons.• It is neutral (has no charge), so it has 6 electrons.

Isotope of carbon• Carbon-14• C-14• 14C• 14 6 C0


neutrons, so it has 8 neutrons.• It is neutral (has no charge), so it has 6 electrons.

What’s the safe answer

here????

Carbon-14 isotope said to Carbon-12 isotope,“Does these neutrons

make my mass look big?

Ion of carbon• Carbon-12• C-12• 12C• 12 6 C+4


neutrons, so it has 6 neutrons.• It is positive (it lost 4 electrons), so it has only 2

electrons.

Are you POSITIVE?

OH NO!!! I think LOST an

ELECTRON!!

A n (- or +)

E Z

E = element symbolZ = atomic number = # protons (identifies element)A = atomic mass = # protons + # neutronsn = charge (+ if fewer electrons than protons) (- if more electrons than protons)

What is the name of the element that has…

• 5 protons

• 17 protons

• 25 protons

• 82 protons

• 92 protons

What is the chemical symbol of…

The atom with• 8 protons

• 11 protons

• 9 protons

How many protons and electrons in atoms of…?

• vanadium?

• nitrogen?

• argon?

• potassium?

What is the chemical symbol of…

The ion with• 8 protons and 10 electrons

• 11 protons and 10 electrons


Write the chemical symbol for the ion with…




Write the chemical symbol for the atom with…

• 5 protons and 6 neutrons



Show 3 ways to write

• The atom with 53 protons and atomic mass 131

How many neutrons are in this isotope?

How many protons, neutrons , electrons…

59 2+ Ni 28


91 4+ Zr 40


140 3+ Ce 58


79 2- Se 34


45 3+ Sc 21


13 4- C 6

Write the complete chemical symbol for the ion with…

84 p125 n80 e


27 p32 n25 e


73 p108 n68 e


31 p39 n28 e

An atom is the smallest particle of an element that retains the chemical identity of the element....

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