Elements and the Periodic Table

Atom

AtomMade of:

● __________________(+)● __________________ (0)● __________________ (-)

○ abbreviated: e-

AtomProtons: located in the ___________Neutrons: located in the ____________Electrons: located in the ______________ ________________________________

In a neutral atom......the # of protons = the # of electrons

A Cloud of Electrons____________ move within a sphere-shaped region surrounding the nucleus

Atoms and ElementsAn element can be identified by the number of _____________ in the nucleus of its atoms.

___________ = the # of protons in its nucleusExample: Every helium atom has 2 protons…

...its atomic number is 2

Atoms ...and all of these numbers... _______________ = atomic numberNeutrons = mass number - atomic numberElectrons = atomic number (in a neutral atom)_________________ = protons + neutrons

“Mass number” = “atomic mass” = “atomic weight”

Atoms ...and all of these numbers...

If necessary, round the atomic mass to the nearest whole number for calculations

IsotopesAlthough all atoms of an element have the same number of protons (ex: all helium atoms have 2), their number of ________ can vary.

__________: atoms with the same number of protons and a different number of neutrons

IsotopesAn isotope is identified by its mass number (which is the sum of the ______ and ______ in the nucleus of an atom)

ModelsBecause atoms are so _________, scientists create models to describe them.The history of it all…

Democritus (400 BC)● Proposed that matter was

composed of tiny ____________ particles

● He called them “______” meaning uncut/indivisible

● Greek: atomos

John Dalton (1808)● _________

_________ Model○ Dalton said that atoms

are “uniform, tiny, solid spheres”

J.J. Thomson (1897)● _________________ Model● Thomson discovered the

____________ (the negative particles) through experiments with electrical current (a flow of charged particles)○ this was the first evidence that atoms

are made of even smaller particles

J.J. Thomson

● Plum Pudding Model

○ Thomson knew that an atom was ____________■ Now, Thomson knew that negative particles

definitely existed, so he theorized that positive particles must have existed, too

Ernest Rutherford (1911)● Nuclear Model

○ discovered the nucleus through experiments with gold foil

○ the nucleus was a ________, ________charge in the center of the atom

○ theorized that the electrons must orbit randomly around this nucleus

○ concluded that the atom is mostly ________space

Ernest Rutherford● ____________ Model

Niels Bohr (1913)● �Planetary Model

○ Bohr agreed with Rutherford’s model of a _________ surrounded by a large volume of space.

○ Bohr’s model focused on ___________○ Bohr theorized that electrons move in

circular orbits within specific energy levels

Niels Bohr● __________ Model

○ like planets around the sun

Erwin Schrodinger (1926)● ____________ Model

○ Theorized that electrons move in a less predictable way…. within orbitals

○ ___________: a region around the nucleus where electrons are likely to be found

Erwin Schrodinger

● Electron Cloud Model○ dots represent

_____________ of finding an electron… not actual electrons

James Chadwick (1932)● Neutron Model

○ Chadwick discovered the ____________: the neutral particles in the nucleus of an atom

Today...The current atomic model results from work done from the 1920’s to the present. Electrons form a negatively charged cloud around the nucleus. It is impossible to determine exactly where an electron is at a given time.● How is a moving propeller similar to an

electron cloud?

Organizing the Elements

VocabAtomic massPeriodic tableChemical symbolPeriodGroup

Dmitri Mendeleev ● As of 1869, a total of

______ elements had been discovered.

● Mendeleev discovered a set of patterns that applied to the elements and created the first periodic table

Dmitri Mendeleev● Mendeleev noticed that a pattern of

properties appeared when he arranged the elements in order of increasing ________ _________○ atomic mass: the average mass of all the isotopes

of that element● Properties of elements repeated

Dmitri Mendeleev● Mendeleev found that arranging the known

elements in _________ led to a few blank spaces.○ Mendeleev predicted that the blank spaces would be

filled by elements that had not yet been discovered… and he was right… they were later discovered

Periodic Table● In the modern periodic table used today, the

properties of elements repeat in each ____ (row) of the table○ periodic means “in a regular, repeated pattern”

● In 1913, the periodic table was changed a little...now the elements are arranged by their _____________(not atomic mass)○ some of the patterns became even more regular

Periodic Table

Mendeleev’s Table

Modern Table

Periodic Table● a square for each element includes:

○ atomic number○ _______________○ name○ _______________

Periodic Table● __________ (row)● ________ (vertical)

○ also called a ________

● The properties of an element can be predicted from its location in the periodic table

Period and Group numbers GroupsThe “A” group numbers represent the number of valence electrons in each atom.

__________ ________: an electron in the outermost shell of an atom

Valence electron Helium is an exception….will talk about this in a later slide Remember

Elements:● can be solids, liquids, gases● can be ______, _______, _________● are arranged in families/groups and

periods (rows) based on their properties

Quick review1. atomic number?2. atomic mass?3. # protons?4. # electrons?5. # neutrons?

In an atom, where is the location of the:

1. electrons?2. protons?3. neutrons?

Metals

VocabMetalMalleableDuctileConductivityReactivityCorrosionAlkali MetalAlkaline Earth MetalTransition MetalAlloyParticle Accelerator

ActivityWhy use aluminum?1. Examine several aluminum objects2. Compare shape, thickness, and appearance3. For what purpose is each object used?4. Use your observations to list as many properties of

aluminum as you can.5. Infer why aluminum was used to make each object.

Metals Metals● Physical properties

○ shiny (high ____________)○ malleable○ ductile○ conductive

● Chemical properties○ reactive

________: the destruction of a metal due to reactivity

Alkali Metal Family● Group _______● Highly, violently

reactive● Have ____ valence

electron, which is easily lost

Alkaline Earth Metal Family● Group _______● React easily, but

not as violently as Group 1

● Have ____ valence electrons

Transition Metal Family● Elements in

groups _______● Good conductors● Less reactive● Number of

valence electrons vary

Metals in mixed groups● These

teal-color-coded elements in groups 13-15 are also metals

● Even less ___________

Lanthanide Series● _______ row at bottom

of periodic table● soft, malleable, shiny,

conductive● They are mixed with more

common metals to make alloys: a mixture of a metal with at least one other element, usually another metal

Actinide Series● ______ row at bottom

of periodic table● only 4 of them occur

naturally on Earth● most created artificially● very ________, break

apart quickly

Synthetic elements● Elements with atomic numbers > ___● Not found naturally on Earth● Instead, elements that follow uranium are

made, or synthesized, when nuclear particles are forced to crash into one another

● ______________ move nuclei faster and faster until they reach high speeds and crash into one another to combine new nuclei

Nonmetals and Metalloids

VocabNonmetalDiatomic moleculeHalogenNoble GasMetalloidSemiconductor

Nonmetals● ____________: an

element that lacks most of the properties of a metal

● Poor _____________● Reactive with other

elements● Most solid nonmetals

are dull and ________

Nonmetals● Physical properties

○ 10 of 16 are gases at room temperature○ dull (not shiny, low luster)○ brittle (not ____________ or _____________)○ poor conductors

● Chemical properties○ reactive

Some exist as a ____________________: consists of two atoms (ex: N2)

More families (groups)

Boron Family● Group ___● __ valence

electrons

Carbon Family● Group ___● __ valence

electrons

Nitrogen Family● Group ___● __ valence

electrons

Oxygen Family● Group ___● __ valence

electrons

Halogen Family● Group ___● __ valence

electrons● Very

reactive!

Noble Gases● Group ___● __ valence

electrons with the exception of Helium--which only has 2 electrons (atomic number is 2), however it is considered a noble gas because it’s outer shell is “filled”

● Unreactive

Hydrogen● It’s chemical properties differ very

much from those of other elements, so it really cannot be grouped into a family

● Gas (upper left-hand corner)

● # protons? ______● # electrons? ______● # neutrons? ______

Metalloids● they have some

characteristics of both _________ and ______________

● brittle, hard, somewhat reactive, varying conductive ability

● they are ____________: substances that can conduct under some conditions, but not under other conditions

We’ve talked about a lot...1. atomic structure

a. protons, neutrons, electrons2. atomic theory and models (history of discoveries)3. periodic table

a. metals, nonmetals, metalloidsb. groups, periodsc. family names of elements

Quick review