Chapter Three

Chapter ThreeChapter ThreeAtomic Structure

and the Periodic Table

Chapter 3 | Slide 2

Atomic Structure and the Periodic Table cont’d

Recall our understanding of an element.Element is matter that ______ be broken down into

a simpler substance by ________ or _________ means.

Recall our understanding of an atom.Atom is the ________ particle of an element that can

exist and still have the properties of the element.

Chapter 3 | Slide 3


Now we will discuss ATOMIC STRUCTURE and Sub-Atomic Particles

An atom is composed of a _______ and an area called the electron _____» The nucleus is very small compared to the size of the

atom » The nucleus contains the _______ (+) and the _______» The __________ (-) are constantly moving around in the

electron cloud» In a neutral atom, the number of electrons (-) is

_______ to the number of protons (+)

Chapter 3 | Slide 4

←Fig. 3.1 Nuclear Model of the AtomThe protons and neutrons of an atom are found in the central nuclear region, or nucleus, and the electrons are found in an electron cloud outside the nucleus.


Chapter 3 | Slide 5


Electron Proton Neutron

Charge -1 +1 0

Actual Mass (g)

9.109 X 10-28 1.673 X 10-24 1.675 X 10-24

Relative Masse = 1 mass unit

1 1837 1839

Chapter 3 | Slide 6


Atomic Symbols

XQA

Z

Mass number = number of protons + number of neutrons

Atomic number = number of protons

Charge = number of protons – number of electrons

Chapter 3 | Slide 7


# _________ = Atomic Number Z

Atoms have no charge, # __________ = # __________ = Z

# Neutrons = ______ Number (A) - # _________ (Z)

Chapter 3 | Slide 8


Electrons are arranged around the nucleus of an atom

Electrons can be _____ to, _______ from or _______ with other atoms

When lost or gained, atoms become _______ (ions)Lost electrons result in _____charged ion, ________Gained electrons result in _____ charged ion, _____# Protons in nucleus ________ changes, _________

arrangement determine chemical properties

Chapter 3 | Slide 9


Atomic Symbol vs Periodic Table

Ca2+40

20

20

Ca40.08

Chapter 3 | Slide 10


• How many electrons, neutrons, and protons are in the following particles?

# protons #electrons #neutrons40Ca40Ca2+

14C

12C



# Protons remains constant

# Neutrons can vary

Mass numbers of atoms of same element will vary depending on the # neutrons in the nucleus

Atoms that differ in # neutrons are called Isotopes



Most elements have naturally occurring __________Number of isotopes can range from two to ten

Example: Silicon, Si exists in three isotopic formsAll Si atoms have 14 protons and 14 electronsMost, 92.21% contain 14 neutrons Some, 4.70% contain 15 neutronsSome, 3.09% contain 16 neutrons



They have the following notations

Si2928

14Si Si

141430



The additional neutrons in the nucleus may have very slight effects on the chemical properties of the element, and some measurable effects on some physical properties such as melting points, boiling points and Densities. See Chemical Connections on pg 55 in text.



The atomic mass is expressed in atomic mass unitsamu

• atomic mass unit• Defined as 1/12th the mass of 12C• 1 amu = the mass of 1 proton or 1 neutron

The atomic mass that is found on the periodic table or used for calculations is a weighted average of the atomic masses for the isotopes



• To get the average mass of an element, you must add together the mass contributions of each different isotope» % abundance x isotopic mass = mass contribution

• Calculate the average atomic mass of Chlorine if 75.53% of the atoms are 35Cl (34.97 amu) and 24.47% of the atoms are 37Cl (36.97 amu).

(0.7553 x 34.97 amu) + (0.2447 x 36.97 amu) = 35.46 amu





→ Table 3.2

Isotopic Data for Elements with Atomic Numbers 1 through 12



Early 1800s, scientists searched for some order in the chemical information known at that time

Certain elements had properties that were very similar to those of other elements

Method or Arrangement was sought that would be consistent with this information



John Newlands (1865) Arranged elements in order of increasing atomic massWhen he did this, he noticed that there were chemical and

physical properties that repeated every eight elements“law of octaves”



→ Fig. 3.2 Mendeleev constructed a periodic table as part of his effort to systemize chemistry.

Edgar Fahs Smith Collection, University of Pennsylvania Library



Dmitri Mendeleev and Julius Lothar Meyer independently proposed ideas or relationships regarding the periodicity of __________ and increasing atomic ________ or atomic _________.

Modern Periodic Law states that when elements are arranged in order of increasing atomic number, elements with similar chemical properties occur at periodic or regularly recurring intervals.


Novastock/PhotoEdit

Atomic Structure and the Periodic Table

→ CO 3.1 Music consists of a series of tones that build octave after octave. Similarly, elements have properties that recur period after period.




Elements with similar chemical properties are positioned in _________ ___________

These _________ _________ are called ________The ____________ ______ of elements are called

____________

Note the _________ are numbered sequentially 1-7The ________ are identified by two notations, using

Roman numerals and letters, or numbered sequentially 1-18





Also note that Element 72 follows Element 57, as does Element 104 follows Element 89

The missing elements 58 through 71 and 90 through 103 are located in two rows at the bottom of the periodic table. Positioned here for convenience. See the periodic table in the next slide with these rows

positioned where they should be located.



Fig. 3.4 In this periodic table, elements 58 through 71 and 90 through 103 are shown in their proper positions.




Common Names for some GroupsGroup IA – Alkali Metals, excluding H

Soft, shiny and readily react with water

Group IIA – Alkaline earth metalsSoft, shiny and moderately reactive toward water

Group VIIA – HalogensReactive, colored, gases at or slightly above room temperatures

Group VIII – Nobel GasesGenerally unreactive, that undergo few, if any, chemical reactions





(a) Some familiar metals are aluminum, lead, tin, and zinc.

(b) Some familiar nonmetals are sulfur, phosphorus, and bromine.

Fig. 3.5



← Fig. 3.6 This portion of the periodic table shows the dividing line between metals and nonmetals.



Electrons are arranged around the nucleus of an atom

Electrons can be lost to, gained from or shared with other atoms

When lost or gained, atoms become charged (ions)Lost electrons result in + charged ion, cationGained electrons result in – charged ion, anionInference: Electrons are special and we will

learn are related to the chemical properties of an element



• The space outside the nucleus in an atom is called the ___________ ____________» The _________ ________ is subdivided into

different ___________ (positioned according to energy each electron possesses • Shells are subdivided into ____________

› Subshells are subdivided into __________○ Each orbital contains _____ electrons



• Electron Shell» A region of space about a nucleus that contains electrons that have

approximately the same energy and that spend most of their time approximately the same distance from the nucleus

• 1st shell» Can contain up to 2 electrons

• 2nd shell» Can contain up to 8 electrons

• 3rd shell» Can contain up to 18 electrons

• 4th shell» Can contain up to 32 electrons

• Any shell can contain up to 2n2 electrons, where n is the shell number



• Subshell» A region of space within an electron shell that contains

electrons that have the same __________» Four different kinds of subshells: s, p, d, and f» Shell 1: contains s subshell» Shell 2: contains s and p subshells» Shell 3: contains s, p, and d subshells» Shell 4: contains s, p, d, and f subshells


→ Fig. 3.7The number of subshells within a shell is equal to the shell number.




• Orbital» Region of space where two electrons are found» Have different shapes depending on which subshell

they are in (shape of region of space not electrons)» There are a different number of orbitals in each kind of

subshell• In an s subshell, there is 1 orbital• In a p subshell, there are 3 orbitals• In a d subshell, there are 5 orbitals• In a f subshell, there are 7 orbitals



Fig. 3.8 An s orbital has spherical shape; a p orbital has two lobes; a d orbital has four lobes; and an f orbital has eight lobes.



Fig. 3.9Orbitals within a subshell differ mainly in orientation.



• There are ____ electrons in each ________» The electrons move around in the __________» One of the electrons spins __________» One of the electrons spins ______________________




• Electron configurations tells us in which subshells the electrons for an element are located.

• Three rules:» 1. Electrons fill orbitals starting with lowest energy first» 2. There can be no more than 2 electrons in any orbital,

and those electrons must have different spins » 3. For orbitals in the same subshell, electrons fill each

orbital singly before any orbital gets a second electron



←Fig. 3.10The order of filling various electron subshells. Subshells of different shells “overlap.”

How will you remember the order?



→ Fig. 3.11The order of filling various electron subshells with electrons follows the same order given by the arrows in this diagram.



Writing Electronic ConfigurationsH 1s1 He 1s2

Li 1s2, 2s1 Ne 1s2, 2s2, 2p6

Na 1s2, 2s2, 2p6, 3s1 Ar 1s2, 2s2, 2p6, 3s2, 3p6

K 1s2, 2s2, 2p6, 3s2, 3p6, 4s1 K [Ar] 4s1

Kr 1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10, 4p6 Kr [Ar] 4s2, 3d10, 4p6



Electronic Configurations of Transition Elements

Fe 1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d6

Br 1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10, 4p5

Pb 1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10, 4p6, 5s2, 4d10,5p6, 6s2, 4f14, 5d10, 6p2



• Which of the following electron configurations is correct for» A) » B) » C) » D) » E)



Give the symbol of the element that has:

A. [Ar]4s2 3d6

B. Four 3p electrons

C. Two electrons in the 4d sublevel

D. The element that has the electron configuration

1s2 2s2 2p6 3s2 3p6 4s2 3d2

1s2 2s2 2p6 3s2 3p6 3d4



Drawing Orbital Diagrams

• First, write out the electron configuration• Start drawing the orbital diagram

» --1 orbital (blanks) for every s subshell» --3 orbitals(blanks) for every p subshell» --5 orbitals (blanks) for every d subshell

• Blanks are circles or squares



Orbital DiagramsLi

Na

Na1+

1s2 2s1 2p 3s 3p

1s2 2s2 2p6 3s1 3p

↑↓ ↑

↑↓ ↑↓ ↑↓ ↑↓ ↑↓

↑↓ ↑↓ ↑↓ ↑↓ ↑↓

1s2 2s2 2p6 3s 3p

↑



Orbital DiagramsN

O

O2-

1s2 2s2 2p3 3s 3p

1s2 2s2 2p4 3s 3p

↑↓

↑↓ ↑↓ ↑↓ ↑ ↑

↑↓ ↑↓ ↑↓ ↑↓ ↑↓

1s2 2s2 2p6 3s 3p

↑↓ ↑ ↑ ↑



← CC 3.3The different colors of fireworks result when heat excites the electrons of different kinds of metal atoms.

William S. Helsel/Getty Images




Electron Configuration and the Periodic LawWe said that elements in the same group have

similar chemical reactivities» Electrons are the subatomic particles involved in

chemical reactions• Which electrons are most likely to be involved in

chemical reactions?» A) those nearest to the nucleus» B) those farthest from the nucleus » C) all are equally likely to be involved



• What differentiates one family from another?» Let’s look at the electron configurations (valance electron

configurations) of the alkali metals to find out.

• Li• Na• K• Rb• Cs• Fr



• Elements with similar properties have the same type of distinguishing electron! (_________ electrons)• The last electron added to the electron configuration for

an element when electron subshells are filled in order of increasing energy

• It is also the one that causes an element’s electron configuration to differ from that of the element immediately preceding it in the periodic table



Chapter Three

Documents

periodic tableatomic

periodic table contdthey

periodic table contdrecall

periodic table contdhow

periodic table contdnow

periodic table contdelectrons

periodic table contdfig

neutronsatomic structure