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4.4  Atomic Number and  Mass Number 4.4  Atomic Number and  Mass Number

4.4 Atomic Number and Mass Number - PowerPoint Presentation

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4.4 Atomic Number and Mass Number - PPT Presentation

All atoms of an element have the same number of protons and the same atomic number Learning Goal Given the atomic number and the mass number of an atom state the number of protons neutrons and electrons ID: 633814

protons number atom atomic number protons atomic atom electrons mass neutrons atoms element nucleus table periodic neutral 207 study

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Slide1

4.4 Atomic Number and Mass Number

All atoms of an element have the same number of protons and the same atomic number.

Learning Goal Given the atomic number and the mass number of an atom, state the number of protons, neutrons, and electrons.Slide2

Atomic Number

The

atomic number is a whole number specific for each element. is the same for all atoms of an element.is equal to the number of protons in an atom.appears above the symbol of an element in the periodic table.11Na

Atomic number

SymbolSlide3

Atomic Number = Protons in an Atom

Atomic number = number of protons—for example,

the atomic number of H is 1; every H atom has one proton.the atomic number of C is 6; every C atom has six protons.the atomic number of Cu is 29; every Cu atom has 29 protons.Core Chemistry Skill Counting Protons and NeutronsSlide4

Atomic Number = Protons in an Atom

All atoms of lithium

(left) contain three protons, and all atoms of carbon (right) contain six protons. Slide5

Atoms are Neutral

For neutral atoms, the net charge is

zero. number of protons = number of electronsAluminum has 13 protons and 13 electrons. The net (overall)charge is zero. 13 protons (13+) + 13 electrons (13–) = 0Slide6

Study Check

Use the periodic table to fill in the atomic number, number of protons, and number of electrons for each of the following elements:

ElementAtomic NumberProtons

Electrons

N

Zn

SSlide7

Solution

Use the periodic table to fill in the atomic

number, number of protons, and number of electrons for each of the following elements:

Element

Atomic

Number

Protons

Electrons

N

7

7

7

Zn

30

30

30

S

16

16

16Slide8

Mass Number

The mass number

represents the number of particles in the nucleus.is equal to the number of protons + the number of neutrons.is always a whole number.does not appear in the periodic table.Slide9

Composition of Some Atoms of Different ElementsSlide10

Study Tips: Protons and Neutrons

Number of

protons = atomic numberNumber of protons + neutrons = mass numberNumber of neutrons = mass number – atomic numberNote: Mass numbers are given for specific isotopes only.Slide11

Study Check

An atom of lead (Pb

) has a mass number of 207. A. How many protons are in the nucleus?B. How many neutrons are in the nucleus?C. How many electrons are in the atom?Slide12

Solution

An atom of lead (Pb) has a mass number of 207.

A. How many protons are in the nucleus? atomic number = 82; number protons = 82B. How many neutrons are in the nucleus? mass number – number protons = number neutrons 207 – 82 = 125 neutronsC. How many electrons are in the atom? An atom is neutral, which means that the number of electrons is equal to the number of protons. An atom of Pb has 82 protons and 82 electrons.