Post on 26-Mar-2021
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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