Physical Physical ScienceScience

Chapter 18Chapter 18Atoms and BondingAtoms and Bonding

Dmitri Mendeleev - 1869Dmitri Mendeleev - 1869

Mendeleev was born in Siberia, Mendeleev was born in Siberia, Russia in the year 1834. He died Russia in the year 1834. He died in 1907in 1907

He was a professor of Chemistry He was a professor of Chemistry at the St. Petersburg University.at the St. Petersburg University.

– Trying to explain to his students how Trying to explain to his students how elements had similar properties, he elements had similar properties, he started organizing the elements into started organizing the elements into rows and columnsrows and columns

He observed that some elements He observed that some elements have similar chemical & physical have similar chemical & physical propertiesproperties

The first periodic table was The first periodic table was organized by atomic massorganized by atomic mass– The masses were compared to The masses were compared to

Hydrogen, the lightest known Hydrogen, the lightest known element at the time.element at the time.

The modern Periodic Table is The modern Periodic Table is organized by Atomic numberorganized by Atomic number

Atomic Models in HistoryAtomic Models in History DemocritusDemocritus, Greek philosopher, , Greek philosopher,

around 400 BC used the term around 400 BC used the term ““atomosatomos” which means “indivisible-” which means “indivisible-unbreakable” to describe (where we unbreakable” to describe (where we get the word “atom”)get the word “atom”)

John DaltonJohn Dalton, 1808 – very similar to , 1808 – very similar to Democritus said atoms were like Democritus said atoms were like solid ballssolid balls

JJ Thomson, JJ Thomson, 1897 – described the 1897 – described the atom as a positively charged sphere atom as a positively charged sphere with negatively charged electrons with negatively charged electrons embedded inside to create a embedded inside to create a neutrally charged particle. Often neutrally charged particle. Often described as a described as a muffin w/ berries muffin w/ berries scattered throughout.scattered throughout.

Democritus

John Dalton

JJ Thomson

RutherfordRutherford, 1911 – refined Dalton’s , 1911 – refined Dalton’s theory & stated atom is mostly theory & stated atom is mostly empty space and the empty space and the negativelynegatively charged electrons charged electrons randomlyrandomly orbitorbit the the positivelypositively charged charged nucleusnucleus..

BohrBohr, 1913 – Said electron , 1913 – Said electron NOT NOT random random but in but in specific layers specific layers or or energy levels. energy levels. Increasing in energy Increasing in energy the farther from the nucleusthe farther from the nucleus

ChadwickChadwick, 1932 – realized the mass , 1932 – realized the mass of the atoms didn’t correspond to of the atoms didn’t correspond to the mass suggested by Bohr’s the mass suggested by Bohr’s model. He discovered the neutron model. He discovered the neutron and determined they were in the and determined they were in the nucleus with the protons nucleus with the protons

Modern TheoryModern Theory, present – shows , present – shows electrons not in orbits but specific electrons not in orbits but specific cloudsclouds, each having their own level , each having their own level of energy of energy

Atomic Models in HistoryAtomic Models in History

Ernest Rutherford

Neils Bohr

Chemical BondsChemical Bonds A A chemical bond chemical bond forms between two atoms when valence forms between two atoms when valence

electrons move between themelectrons move between them Two main types of chemical bondsTwo main types of chemical bonds

– Covalent BondsCovalent Bonds: occur between atoms when valence : occur between atoms when valence electrons are electrons are sharedshared..

– Ionic BondsIonic Bonds: occur when valence electrons are : occur when valence electrons are transferredtransferred ( (stolenstolen) between atoms ) between atoms

– A third type of bond between atoms are A third type of bond between atoms are hydrogen bondshydrogen bonds

Ionic BondingIonic Bonding When an atom gains or loses and electron or two When an atom gains or loses and electron or two

they no longer have a neutral charge. A charged they no longer have a neutral charge. A charged atom is called an “Ion”atom is called an “Ion”

An Ion w/ extra electrons makes it negatively An Ion w/ extra electrons makes it negatively charged, this an Anioncharged, this an Anion

An Ion w/ more protons than electrons makes it An Ion w/ more protons than electrons makes it positively charged & is called a Cation.positively charged & is called a Cation.

A “+” ion (A “+” ion (CationCation) is attracted to a (-) ion () is attracted to a (-) ion (AnionAnion) ) just like two magnets are attracted to each other just like two magnets are attracted to each other

When ions get close enough together they form an When ions get close enough together they form an chemical bond – an Ionic Bond!chemical bond – an Ionic Bond!

Ding-a-Ling! Ding-a-Ling!

A metal and a nonmetal will form Ionic Bonds when

chemically bonded together!!Naming Ionic

compounds1.The metal is named first2.If the anion is an element, the end of its name is changed ti “ide”3.Polyatomic ions usually keep their namesNTK - “Polyatomic” ions

HCO3-1 Bicarbonate

NO3-1 NitrateO-2 OxideSO4

-2 SulfateCO3

-2 Carbonate

Counting Atoms in an Counting Atoms in an EquationEquation

If no subscript present it is assumed to be 1 atomIf no subscript present it is assumed to be 1 atom If elements in brackets or parenthesis, treat same If elements in brackets or parenthesis, treat same

as in math.as in math. Coefficients multiple the entire molecule atomsCoefficients multiple the entire molecule atoms You must add all reactant molecules together & You must add all reactant molecules together &

compare w/ all molecules in the products compare w/ all molecules in the products

Ca3(PO4)2

Ca=3P=2O=8

2Ca3(PO4)

2

Ca=6P=4

O=16

CaCl2

Ca=1Cl=2

It’s best to list the # of atoms under the molecules as we are doing in these examples

Use this to help with worksheet pg. 51 –

Number of Atoms in a Formula !!!

Writing Binary FormulasWriting Binary Formulas Ions build strong bonds that have a Ions build strong bonds that have a net electrical charge of 0 net electrical charge of 0

(zero)(zero) Remember the Remember the CationCation (+ ion) is listed 1 (+ ion) is listed 1stst, the , the AnionAnion (- ion) is 2 (- ion) is 2ndnd

You write how many of the ions you need as subscripts.You write how many of the ions you need as subscripts. A Sodium ion, A Sodium ion, NaNa++ will bond with a Chlorine ion, will bond with a Chlorine ion, ClCl-- NaClNaCl A Barium ion, A Barium ion, BaBa+2+2, will bond with a Flourine ion, , will bond with a Flourine ion, FF-- BaFBaF22

How many Flourine ions do you need to balance the +2 charge on the Ba ion? How many Flourine ions do you need to balance the +2 charge on the Ba ion? … you need 2 and you write the formula as a subscript on the Flourine ion.… you need 2 and you write the formula as a subscript on the Flourine ion.

A Silver ion, A Silver ion, AgAg++ will bond with an Oxygen ion, will bond with an Oxygen ion, OO-2-2 AgAg22OO– You need 2 You need 2 AgAg++ to balance the O to balance the O-2-2 charge charge

A Nickel ion, A Nickel ion, NiNi+3+3 will bond with an Oxygen ion, will bond with an Oxygen ion, OO-2-2 NiNi22OO33

– With this bond you need 2 NickelWith this bond you need 2 Nickel+3+3’s that have a total of a +6 ’s that have a total of a +6 electrical charge to balance 3 Oxygenelectrical charge to balance 3 Oxygen-2-2’s that will have a total of -6 ’s that will have a total of -6 electrical charge. A +6 added to a -6 = 0electrical charge. A +6 added to a -6 = 0Use this to help with

worksheet pg. 54 – Writing Binary Formulas !!!

Covalent BondingCovalent Bonding When valence electrons are “shared”, When valence electrons are “shared”,

covalent bonds are formedcovalent bonds are formed They are generally weaker than Ionic bondsThey are generally weaker than Ionic bonds The number of bonds an atom can form is The number of bonds an atom can form is

equal to the number of electrons needed to equal to the number of electrons needed to reach the required 8 valence electronsreach the required 8 valence electrons

Hydrogen needs only 1 to be like Helium Hydrogen needs only 1 to be like Helium that has 2 and fills its “S” orbit.that has 2 and fills its “S” orbit.

Ding-a-Ling! Ding-a-Ling!

Two or more nonmetals will form

Covalent Bonds when chemically bonded

together!!

Carbon can form 4 bonds

Chlorine can form 1 bond

Oxygen can form 2 bonds

Nonpolar Covalent Bonds - Equal sharing of electronsNonpolar Covalent Bonds - Equal sharing of electrons Polar Covalent Bonds – an unequal sharing of electronsPolar Covalent Bonds – an unequal sharing of electrons Some atoms pull stronger on the “shared” electrons than other atomsSome atoms pull stronger on the “shared” electrons than other atoms

– These electrons move closer to these atoms and they become more negatively chargedThese electrons move closer to these atoms and they become more negatively charged– The atom that the shared electrons move away from become slightly positively chargedThe atom that the shared electrons move away from become slightly positively charged

Polar or Nonpolar Covalent Polar or Nonpolar Covalent BondingBonding

Carbon Tetrachloride

Hydrogen BondsHydrogen Bonds The weak attractive force of a hydrogen The weak attractive force of a hydrogen

atom and a negatively charged part of atom and a negatively charged part of another molecule/atom. another molecule/atom.

Here’s a little Here’s a little secret….Quarks!secret….Quarks! ProtonsProtons and and NeutronsNeutrons can be broken into smaller can be broken into smaller

elemental particles called quarks!elemental particles called quarks! QuarksQuarks – the building blocks of subatomic particles. These – the building blocks of subatomic particles. These

“FLAVORS” come in 3 pairs, so there are 6 different “FLAVORS” come in 3 pairs, so there are 6 different quarks: Up, Down, Top, Bottom, Charmed and Strangequarks: Up, Down, Top, Bottom, Charmed and Strange

A A quarkquark has a mass of 1/3 AMU has a mass of 1/3 AMU An An Up quark Up quark has a 2/3 positive charge and a has a 2/3 positive charge and a Down quarkDown quark

has a 1/3 negative chargehas a 1/3 negative charge A proton is made up of 2 “up” quarks and 1 “down” quarkA proton is made up of 2 “up” quarks and 1 “down” quark A neutron is made of 2 “Down” quarks and 1 “Up” quark.A neutron is made of 2 “Down” quarks and 1 “Up” quark.

The Neutron

The Proton

The electron is also an elementary The electron is also an elementary particle known as a “Lepton” & particle known as a “Lepton” & has a mass 1/612 that of a quarkhas a mass 1/612 that of a quark

No Mas!!No Mas!!No Mas!!No Mas!!

We be done!!We be done!!