Atomos, Teorías Atómicas, Teoría Cuántica, Masa Atómica e Isotopos

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Chapter 4 Atoms and Elements

4.3

The Atom

Copyright © 2008 by Pearson Education, Inc.Publishing as Benjamin Cummings

Atom- smallest particle of an element that retains the characteristics of that element

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4.1Elements and Symbols


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Elements are

• Pure substances that cannot be separated into simpler substances by ordinary laboratory processes.

gold carbon aluminum

Elements


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Sources of Some Element Names

Some elements are

named for • planets,• mythological

figures,• minerals, • colors,• scientists, and• places. Copyright © 2008 by Pearson Education, Inc.

Publishing as Benjamin Cummings

Table 4.1

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A symbol• Represents the name of an element.• Starts with a capital letter.

Examples:

C carbon Co cobaltN nitrogen Ca calciumF fluorine Al aluminum O oxygen Mg magnesium

Symbols of Elements

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Select the correct symbol for each:A. calcium

1) C 2) Ca 3) CA

B. sulfur 1) S 2) Sl 3) Su

C. iron 1) Ir 2) FE 3) Fe

Learning Check

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Select the correct symbol for each:

A. calcium

2) Ca

B. sulfur

1) S

C. iron

3) Fe

Solution

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Select the correct name for each symbol:A. N

1) neon 2) nitrogen 3) nickel

B. P 1) potassium 2) phosphorus 3) phlogiston

C. Ag 1) silver 2) agean 3) gold

Learning Check

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Select the correct name for each:

A. N

2) nitrogen

B. P 2) phosphorus

C. Ag

1) silver

Solution

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Subatomic Particles

Atoms contains subatomic particles• Protons positive (+) charge.• Neutrons are neutral.• Electrons negative (-) charge.

( very small mass)

Like charges repel and unlike charges attract.


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Structure of the Atom

An atom consists• nucleus (protons and

neutrons)• large empty space

around the nucleus (electrons)


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Particles in the Atom

Copyright © 2008 by Pearson Education, Inc. Publishing as Benjamin Cummings

Table .5

From page 107 do exercises 4.15 to 4.22 (don´t do 4.17)

Newest - the atom has no definite shape and electrons don´t have precise orbits, they are in clouds

It´s a theory based on the quantum. A quantum is a specific amount of energy

that can cause an electron to change its level.

A quantum of energy move an electron up in its energy level.

And... a quantum of energy is released when an electron moves down an energy level.

The 4 quantum numbers describethe electron´s energy level shape.

N= level. distance from nucleus

L=shape geometry. Sublevel (s,p,d,f)

M= magnetic #, orientation of the electron

S= spin of e-

Electron configuration

Start at the beginning of each arrow, and follow it all to the end

1st Quantum # =n= the # of sub-levels

If n=1 one sublevel (s) n=2 2 sublevels (s, p)

n=3 3 sub-levels (s, p, d) n=4 4 sub-levels (s, p, d, f)

Electron Configuration

How electrons are distributed among the energy levels .

He:1s2 The large number "1" refers to the principle

quantum number "n" (the energy level). electrons occupy an "s" or spherical orbital. The exponent "2" is the total number of

electrons in that orbital

Sublevel # of orbitals Maximum number of electrons

s 1 2

p 3 6

d 5 10

f 7 14

The valence shell or outer shell (highest energy level) is the responsible for how an element reacts to form compounds.

Find the electron configuration of: Cl, Na, Cr, Ne, Fe

Principles of Aufbau, Pauli’s exclusion and Hund’s rule to write electronic configurations 3 Rules for filling orbitals Aufbau principle: Electrons enter the orbital of lowest

energy first Pauli exclusion principle: Only 2 electrons in an orbital

and they cannot have the same spin, up or down. (PS: S orbitals are spheric, P orbitals are like dumbbells )

Hund´s Rule: When electrons occupy equal energy levels, one electron enters each orbital until all the orbitals contain one electron with parallel spin. Then you can add more electrons to the orbital with opposite spin.

Using the 3 rules do the electron conf, of Mg, O , Cu, and Cr

Return to previous page Aufbau Diagram of Principal Energy Levels, Sublevels and Orbitals

7s 6p 5d

4f

6s 5p 4d

5s 4p

3d 4s 3p

3s 2p

2s

1s Each box represents an atomic orbital which can hold up to 2 electrons with opposite spins.

http://www.montvilleschools.org/highschool/science/edorff/chemistry/Handouts.htm

24 Mg __ ___ __ __ __ __ 1s2 2s2 2p6 3s2

16 O __ __ __ __ __ 1s2 2s2 2p6

63 Cu __ __ __ __ __ __ __ __ __ __ 1s2 2s2 2p6 3s2 3p6 4s2

___ ___ ___ ___ ___

3d10

12

8

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Ions

Ion: group of atoms that has a positive or negative charge; cations - ions with a positive charge: Metals tend to form cations anions - ions with a negative charge. Nonmetals tend to form anions

Table salt, sodium chloride NaCl in water forms the ions: Na+ and Cl- Try to figure out why Na is a cation and Cl is an anion

11 17

23 Na 35 Cl

Do p67 problem Do electron configuration of: Na +1, Cl -1, Mg +2, O-2

Read exercise from page 44, do problems from page 50 # 39-43

Lewis dot diagram

Another way of showing electron configuration is the Lewis or electron dot diagrams.

Write the elements symbol and draw a group of 1-8 dots, which shows the electrons in the outer or valence shell. (for H and He only 2 e- )

example : oxygen you need to know how many electrons are in the valence shell. The

electron configuration of oxygen is 1s2 2s2 2p4

You fill in one valence electron on each side of the elemental symbol,

and then double up as many sides as needed The electrons that are unpaired are the ones that take part in

chemical reactions. Try drawing the dot diagrams for Li, Na, Cl, H, He, B, N , KCl, NH3,

CaBr2, H2O, CH4, AlF3

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4.4

Atomic Number and Mass Number

32S, 33S, 34S, 36S 16 16 16 16


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The atomic number • Is 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.

Atomic Number

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Na

Atomic Number

Symbol

32

Examples:

• Hydrogen has atomic number 1, every H atom has one proton.

• Carbon has atomic number 6, every C atom has six protons.

• Copper has atomic number 29, every Cu atom has 29 protons.

• Gold has atomic number 79, every Au atom has 79 protons.

Atomic Numbers and Protons

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Atomic Models


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State the number of protons in each.

A. A nitrogen atom 1) 5 protons 2) 7 protons 3) 14 protons

B. A sulfur atom 1) 32 protons 2) 16 protons 3) 6 protons

C. A barium atom 1) 137 protons 2) 81 protons 3) 56 protons

Learning Check

35

State the number of protons in each.

A. A nitrogen atom 2) atomic number 7; 7 protons

B. A sulfur atom 2) atomic number 16; 16 protons

C. A barium atom, 3) atomic number 56; 56 protons

Solution

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• An atom of any element is electrically neutral; the net charge of an atom is zero.

• In an atom, the number of protons is equal to the number of electrons.

number of protons = number of electrons

• For example, an atom of aluminum has 13 protons and 13 electrons. The net charge is zero.

13 protons (13 +) + 13 electrons (13 -) = 0

Electrons in An Atom

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Mass Number

The mass number • Represents the number of particles in the nucleus.• Is equal to the

Number of protons + Number of neutrons


Table 4.6

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An atom of zinc has a mass number of 65.

A. How many protons are in this zinc atom?

1) 30 2) 35 3) 65

B. How many neutrons are in the zinc atom?

1) 30 2) 35 3) 65

C. What is the mass number of a zinc atom that has 37 neutrons?

1) 37 2) 65 3) 67

Learning Check

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An atom of zinc has a mass number of 65.A. How many protons are in this zinc atom?

1) 30 (atomic number 30) B. How many neutrons are in the zinc atom?

2) 35 (65 – 30 = 35)

C. What is the mass number of a zinc atom that has 37 neutrons? 3) 67 (30 + 37 = 67)

Solution

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An atom has 14 protons and 20 neutrons.

A. Its atomic number is

1) 14 2) 16 3) 34

B. Its mass number is

1) 14 2) 16 3) 34

C. The element is

1) Si 2) Ca 3) Se

Learning Check

41

An atom has 14 protons and 20 neutrons.

A. It has atomic number 1) 14

B. It has a mass number of 3) 34 (14 + 20 = 34)

C. The element is 1) Si (Atomic number 14)

Solution

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4.5Isotopes and Atomic Mass

24Mg 25Mg 26Mg 12 12 12


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Isotopes

• Atoms of the same element that have same number of protons, but different numbers of neutrons,

so……different mass numbers.

Isotopes

Examples isotopes

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

12C 13C 14C 6 6 6

protons ______ ______ ______

neutrons ______ ______ ______

electrons ______ ______ ______

Learning Check

46

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

12C 13C 14C 6 6 6

protons 6 p+ 6 p+ 6 p+

neutrons 6 n 7 n 8 n

electrons 6 e- 6 e- 6 e-

Solution

Ions

Ion: atom(s) that has a positive or negative charge

cations – ions with a positive charge, give electrons, Metals tend to form cations

anions – ions with a negative charge. receive electrons

, Nonmetals tend to form anions

Table salt, sodium chloride NaCl in water forms the ions: Na+ and Cl -

Try to figure out why Na is a cation and Cl is an anion

Do protons,,neutrons and electrons of : Na +1, Cl -1, Mg +2, O-2

Atomos, Teorías Atómicas, Teoría Cuántica, Masa Atómica e Isotopos

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