Atomic Structure 3.1

Atomic History In 400 BC a Greek Philosopher, Democritus suggested the universe was made of invisible units-- atoms.

1800’s John Dalton’s Theory (Still Accepted) 1.Every element is made of tiny, unique particles called atoms 2.Atoms of different elements can join to form molecules. 1.Every element is made of tiny, unique particles called atoms 2.Atoms of different elements can join to form molecules.

John Dalton’s Theory- Disproved 3.Atoms are the smallest particles and cannot be subdivided. 4.Atoms of the same element are exactly alike in mass 3.Atoms are the smallest particles and cannot be subdivided. 4.Atoms of the same element are exactly alike in mass

JJ Thomson  Credited with discovering negative charged particles called electrons.

Rutherford  Credited with discovering nucleus.  and atoms are mostly empty space.  Credited with discovering nucleus.  and atoms are mostly empty space.

Further Research Finding  Later on, the discovery of protons and neutrons were discovered in the nucleus.  And it was later concluded that all atoms are neutral in charge.  The number of protons and electrons in any atom are always equal.  Later on, the discovery of protons and neutrons were discovered in the nucleus.  And it was later concluded that all atoms are neutral in charge.  The number of protons and electrons in any atom are always equal.

Niels Bohr  Suggested that electrons move around atoms in set paths around the nucleus.  He said each path is an energy level  Suggested that electrons move around atoms in set paths around the nucleus.  He said each path is an energy level

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Today’s Theory  It is impossible to pinpoint an electron’s exact position due to its tremendous speed.  Electrons do not move around in definite paths.  It is impossible to pinpoint an electron’s exact position due to its tremendous speed.  Electrons do not move around in definite paths.

Today’s Theory  Electrons are found in orbitals within energy levels. (s, p, d, and f )  a region in an atom where there is a high probability of finding electrons.  Electrons are found in orbitals within energy levels. (s, p, d, and f )  a region in an atom where there is a high probability of finding electrons.

Today’s Theory  Electrons are now viewed as waves vibrating on a string rather than simple particles.  Wave-Particle Duality Theory  Electrons are now viewed as waves vibrating on a string rather than simple particles.  Wave-Particle Duality Theory

What are atoms?  The smallest part of an element that still has the element’s properties.

Parts of an atom  Nucleus  Proton  Neutron  Electron  Nucleus  Proton  Neutron  Electron Subatomic particles

Nucleus center of an atom positively charged makes up 99.9% of the atom’s mass contains protons and neutrons center of an atom positively charged makes up 99.9% of the atom’s mass contains protons and neutrons

Protons  Charge (+)  Mass is equal to 1 atomic mass unit (amu)  Found in the nucleus  Identifies the element/atom

Neutrons  Charge (0) – neutral  Mass is equal to 1amu  Found in the nucleus  Helps determine mass

Electrons Charge is negative (-) Mass is equal to 0 amu Found outside the nucleus, in the electron cloud

Energy levels  1 st level holds up to 2 e -  2 nd level holds up to 8 e -  3 rd level holds up to 8 or 18 e -  4 th level holds up to 8, 18, or 32 e -  Outer Level holds up to 8 e- (called valence electrons)  1 st level holds up to 2 e -  2 nd level holds up to 8 e -  3 rd level holds up to 8 or 18 e -  4 th level holds up to 8, 18, or 32 e -  Outer Level holds up to 8 e- (called valence electrons)

Valence Electron  The number of electrons in the outermost electron shell.  Most important  The number of electrons in the outermost electron shell.  Most important

A Guided Tour of the Periodic Table 3.2

Periodic Law Properties of elements tend to change in a regular pattern when elements are arranged in order of increasing atomic number.

Periodic Law  Periodic Table is set up by increasing atomic number.  Atomic Number is the # of protons in the atom.  Periodic Table is set up by increasing atomic number.  Atomic Number is the # of protons in the atom.

Average Atomic Mass

Atomic Number tells you number of protons Never Changes for an atom. Appears as a whole # on the periodic table. No two elements can have same atomic #. tells you number of protons Never Changes for an atom. Appears as a whole # on the periodic table. No two elements can have same atomic #.

Atomic Number # of protons Atomic Number

Mass Number  The mass of an atom  Total number of protons plus neutrons in the nucleus of a single atom.  Atoms of the same element won’t always have the same mass number  The mass of an atom  Total number of protons plus neutrons in the nucleus of a single atom.  Atoms of the same element won’t always have the same mass number

Mass Number # of protons # of neutrons Mass #

Isotopes Any atoms having the same number of protons but different number of neutrons. So they also have different mass numbers. Any atoms having the same number of protons but different number of neutrons. So they also have different mass numbers.

Average Atomic Mass  Average mass of all known isotopes for an element  Found on the periodic table as a number with a decimal  Average mass of all known isotopes for an element  Found on the periodic table as a number with a decimal

Atom’s Charge They are neutral. All atoms have the same number of protons and electrons. Charges cancel each other out. They are neutral. All atoms have the same number of protons and electrons. Charges cancel each other out.

Ions  Charged particles.  Form when atoms lose or gain electrons.  They do this so the ions have a full outer shell  Two Types.  Charged particles.  Form when atoms lose or gain electrons.  They do this so the ions have a full outer shell  Two Types.

Cations Positively charged ions. Form when atoms lose electrons. Metals Left side of table Positively charged ions. Form when atoms lose electrons. Metals Left side of table

Cations  # of protons greater than # of electrons  More (+) than (-)  # of protons greater than # of electrons  More (+) than (-)

Na Atom Na + Cation

Anions Negatively charged ions. Form when atoms gain electrons. Nonmetals Right side of table Negatively charged ions. Form when atoms gain electrons. Nonmetals Right side of table

Anions  # of protons less than # of electrons  More (-) than (+)  # of protons less than # of electrons  More (-) than (+)

Cl atom Cl - Anion

Quantifying atoms or ions +1 Protons = 3 Neutrons = 7-3 = 4 Electrons = 3 Electrons = 3 -1 = 2

Families of Elements 3.3

Periodic Table  Periods -a horizontal row of elements. -Tells you the electrons energy level.  Periods -a horizontal row of elements. -Tells you the electrons energy level.

Periodic Table  Groups (families) -a vertical column of elements. -Tells us the # of valence electrons and the elements’ chemical properties.  Groups (families) -a vertical column of elements. -Tells us the # of valence electrons and the elements’ chemical properties.

Types of Elements 1.Metals 2.Nonmetals 3.Semiconductors/metalloid 1.Metals 2.Nonmetals 3.Semiconductors/metalloid

Transition Metals Alkaline Earth Metals Alkali Metals Metalloids Other Metals Non Metals Halogens Nobel Gases Inner Transition Metals

Alkali Metals Group 1  Most reactive metals  one valence e-  Found as compounds (salts) and not elements due to reactivity.  As elements they are soft metals and good conductors.  Most reactive metals  one valence e-  Found as compounds (salts) and not elements due to reactivity.  As elements they are soft metals and good conductors.

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Alkaline-earth Metals Group 2  Less reactive than Alkali  They are also more commonly found as compounds  2 most common are Ca and Mg.  Less reactive than Alkali  They are also more commonly found as compounds  2 most common are Ca and Mg.

Transition Metals Groups 3-12  Less reactive than groups 1 and 2  Good conductors  Less reactive than groups 1 and 2  Good conductors

Transition Metals  All solids with the exception of mercury  Valuable metals (Ag, Au, Pt, Cu, Ni, Fe, Co)  All solids with the exception of mercury  Valuable metals (Ag, Au, Pt, Cu, Ni, Fe, Co)

Non Metals  Are not able to conduct electricity or heat very well.  Found in groups 13-18, with the exception of hydrogen  Are not able to conduct electricity or heat very well.  Found in groups 13-18, with the exception of hydrogen

Carbon  Found as an element (coal, diamond, graphite)  Found in millions of different compounds  Called Organic Compounds  Found as an element (coal, diamond, graphite)  Found in millions of different compounds  Called Organic Compounds

HYDROGEN  It is a gas/nonmetal  A very explosive gas.  It is located in group one because it has one valence electron   It is a gas/nonmetal  A very explosive gas.  It is located in group one because it has one valence electron 

Oxygen and Nitrogen  Oxygen is the most common element found on Earth  Nitrogen most common gas found in the atmosphere  Oxygen is the most common element found on Earth  Nitrogen most common gas found in the atmosphere

Halogens Group 17  Most reactive nonmetals  Form salts with group 1  Used to kill bacteria  Bromine only liquid nonmetal  Most reactive nonmetals  Form salts with group 1  Used to kill bacteria  Bromine only liquid nonmetal

Noble Gases Group 18  Stable and not reactive. (inert)  Don’t form compounds.  They have a full valence shell.  Stable and not reactive. (inert)  Don’t form compounds.  They have a full valence shell.

Metalloids (Semiconductors)  7 elements on the step  Properties of both metals and non- metals.  Silicon the most familiar (computer chips)  7 elements on the step  Properties of both metals and non- metals.  Silicon the most familiar (computer chips)

Inner Transition Metals  Two rows at the bottom  Some are Radioactive ex. Uranium  93 and greater are all manmade  Two rows at the bottom  Some are Radioactive ex. Uranium  93 and greater are all manmade