Unit 2 – Lecture 3

Atomssmallest particle of an element that retains

its chemical propertiescomposed of subatomic particles

protons (p+), neutrons (n0), & electrons (e-)“sub-” = below, less than

Subatomic ParticlesTypes of Subatomic Particles[p+] – positively charged subatomic particle

found in the nucleus of an atomrelative mass = 1 amu [atomic mass unit]

[n0] – non-charged subatomic particle [neutral]found in the nucleus of an atomrelative mass = slightly larger than 1 amunew theories: [p+] + [e-] = [n0] ?

Subatomic Particles – cont’d[e-] – negatively charged subatomic particle

found outside of the nucleus in energy levels [aka e- clouds, e- shells, etc]

no relative mass[actual mass is 1/1936th of 1 amu…]

Quarks?theoretically = smaller particles that

make up (p+), (n0), & (e-)have their own branch of “theoretical

physics”

DiscussWhich subatomic particle is neutral?Which describes a single particle of an

element?Which subatomic particle is negative?Which subatomic particle may or may not

exist?Which is a single particle of a compound?Which subatomic particle is positive?

Elements

Elements – cont’dElements are found on the periodic table in

their natural, neutral statemeaning, they’re neutral = same # of p+ &

e -

Discuss - Oxygenatomic mass?number of protons?atomic number?number of electrons?chemical symbol?number of neutrons?

More PracticeAn atom with 4 protons and 6 neutrons

would:have a mass of…?have an atomic number of…?have … electrons typically?be which element?

Writing Elements - SilverWrite:Chemical SymbolMass Number at the

upper-left of the symbolAtomic Number at the

lower-left of the symbolCharge [if applicable] at the

upper-right hand corner

NOT ALL OF THESE ARE NECESSARYNOT ALL OF THESE ARE NECESSARY

Ag108

47

+4

Counting Particlesp+s = Atomic Number

[17]n0s = Atomic Mass – Atomic Number

[35-17 = 18]e-s = p+s

[17]

Cl3517

Counting Particles – cont’dif e-s differ

called ioncharge is different

more e-s [than normal] = more negative charge

less e-s [than normal] = more positive charge

Counting Particles – cont’dif n0s differ

called isotope“iso-” = equal/same

same chem & phys properties atomic mass on periodic table is average of

isotopes

if p+s differis a different element

Isotopes – Examples

Different Atoms, Same ElementAllotrope – different natural/physical forms of

an element“allo-” = other/differentEx. for Carbon: Graphite, Diamond,

Buckminsterfullerenes [buckyballs]…Ex. for Oxygen: [O2], Ozone [O3]

Allotropes of Carbona. diamondb. graphitec. lonsdaleited. buckyballs [C60 –

buckminsterfullerene]e. C540f. C70g. “amorphous” carbon

[not truly amorphous]h. single-walled

carbon nanotube / buckytube

Allotropes of Oxygen

Electron-Dot Modelsp+s & n0s exist in the nucleuse-s exist in electron/energy shells

around the nucleus“octet rule” - atoms will gain,

lose, or share e-s to become chemically stable [8 e-s in valence shell]valence shell = outer-most shell

e-s in valence shell = valence e-s

Electron-Dot Models

• Draw • Nucleus• Protons• Neutrons

Electron-Dot Models – cont’d

• Draw• Electrons

Electron Levels• *2*• up to 8…

DiscussAtoms are the smallest particle of

elements, compounds, homogeneous mixtures, heterogeneous mixtures

Which subatomic particle has a neutral charge?protons, neutrons, electrons, quarks

What is the dense center of an atom called?protium, nucleus, neutron core, core

DiscussWhich property discerns atoms from one

another?atomic mass, mass number,

atomic number, none of the above

Atomic Number is based on which property of atoms?# of protons, # of electrons,

# of neutrons, total # of particles

DiscussThe total number of nucleons is

atomic mass, atomic number, nucleon count, state of matter

Atoms of an element with different number of neutrons areallotropes, isotopes, megatopes,

gigatropes

Which subatomic particles are not included in calculating Atomic Mass?protons, neutrons, electrons, nucleons

DiscussHow many neutrons are in Oxygen-16, which

has an atomic number of 8? [# denotes mass]4, 6, 8, 10, 12, 14, 16

How many neutrons are in Oxygen-18, which has an atomic number of 8?4, 6, 8, 10, 12, 14, 16

Which subatomic particle has a positive charge?Protons, Neutrons, Electrons, Quarks

How many e-s fit in an atom’s first electron level?

HomeworkComplete - page 13 - # of Atoms in a Formula w/s

DO NOT COMPLETE GRAM FORMULA MASS w/s IN THE MIDDLE OF PAGE 13.

- BOTTOM of pg 13-top of 14 Parts of An Atom [CHART]