Unit 3: Atomic Structure

electron

negative particle outside of the nucleus in the electron cloud

neutron

neutral particle in the nucleus with protons

proton

positive particle in the nucleus

quarks

protons and neutrons are made up of these, the smallest known particles

mass number

tells the number of protons and neutrons in the nucleus of atom (where most of its mass is located)

atomic number

tells the number protons in an atom of the element -used to identify an element -PT arranged by these

valence electrons

the electrons furtherest away from the nucleus and have the most energy

periods

the horizontal rows -all elements in the same period have the same number of energy levels in their electron cloud

If they're in the same group they have similar valence electrons. If they're in the same period they have the same number of energy levels in their electron cloud.

Describe the pattern/shared characteristics of elements in the same group vs. the same period

Bohr Model suggested that the electrons travel in fixed orbits around the nucleus, but the Electron Cloud Model suggested that the nucleus is surrounded by an electron cloud but do not travel in fixed orbits.

Differentiate between the Bohr Model and the Electron Cloud Model.

Metals: shiny, silvery solids, good conductors of heat and electricity, located to the left pf metalloids Nonmetals: gases, or dull brittle solids, poor conductors, right of metalloids (with hydrogen) Metalloids: solids, semi-conductors, in middle of metals and nonmetals

Differentiate between the characteristics of metals, nonmetals, and metalloids. Include their general location on the periodic table.

The electron cloud is the space surrounding the nucleus. Broken down into shells/energy levels. The number of electrons on each level depends on which group the element belongs to. The valence electrons are the electrons in an atom's outermost energy level in the electron cloud. level 1 holds 2 e~, level 2 holds 8, level 3 holds 8, and level 4 holds 18.

Explain the structure of the electron cloud. Include how many electrons are held on each level, where valence electrons are, and which electrons are the craziest.

-Attractive force between the nucleus and electron cloud: this is what holds the atom together -Repulsive force between electrons: what gives the the electron cloud volume -Repulsive force between protons: insane amount of energy holds the nucleus together

Explain the three forces at work that hold an atom together.

In an electrically neutral atom, the number of protons equals the total number of electrons so that the overall charge of the atom is 0.

Explain what it means for an atom to be electrically neutral.

The protons are the same for both, but the neutrons are different. An isotope is most stable when the number of protons and neutrons are the same.

Explain what two isotopes of the same element have in common and what is different about them. Include when an isotope is considered to be the most stable.

They have similar properties because all elements in the same group have the same number of valence electrons.

Explain why elements in the same group have similar properties.

a. boron b. oxygen c. antimony d. helium

Identify each element described below: a. The first element in group 13 b. A period 2 nonmetal with 6 valence electrons c. A metalloid with 71 neutrons d. A gas with 2 valence electrons and 1 energy level in its electron cloud

a. nitrogen group b. alkali metals c. halogens d. noble gases

Identify each group described below: a. Their atoms have 5 valence electrons b. They are the most reactive metals c. They are the most reactive nonmetals d. They do not react in nature

Group 1: Alkali metals, most reactive metals, for metals, reactivity increases as you move down Group 2: Alkaline earth metals Group 3: Rare earth metals Group 3-12: Transition metals Group 17: Halogens, most reactive nonmetals, decrease as you go down Group 18: Noble gases, nonreactive elements

List the names and any special characteristics for groups 1, 2, 3, 3-12, 17, and 18.

1. 400 B.C, Democritus, first to name the atom 2. 1803, John Dalton (solid sphere model), all atoms of an element are identical 3. 1869, Dmitri Mendeleev, developed the first periodic table by atomic mass 4. 1904, JJ Thompson (Plum pudding model), positively charged with particles 5. 1911, Ernest Rutherford (Nuclear model), positive mass in the center and negative particles surround 6. 1913, Henry Moseley/Niels Bohr (Bohr model), electrons travel in fixed orbits 7. 1926, Schrodinger and Heisenberg (Electron cloud model), electrons in shells in the cloud and not fixed orbit

Make a timeline of the discovery of the structure of the atom. Include date, name, and a brief summary of each discovery or model.

Two parts: nucleus and electron cloud Three particles: protons, neutrons, and electrons Nucleus: dense center, positively charged, most mass is here Electron cloud: space surrounding the nucleus, negatively charged, most volume is here

Summarize our current understanding of atomic structure. Include the two parts, where the three particles are located, and where the mass and volume in an atom mainly exist.

a. atomic number b. mass number c. atomic number d. atomic number e. average atomic mass

Which numbers tell you the following: a. the number of protons b. the number of protons and neutrons c. the number of total electrons d. the identity of an element e. the most common form of an element

Hyphen: Lithium-7 Nuclear: 7Li

Write in both hyphen and nuclear notation the most common isotope for lithium.

isotopes

atoms of the same element with different numbers of neutrons -atomic number is the same for both, mass number is different

atom

the smallest particle of an element that still has the properties of that element -simplest form of matter

groups

the vertical columns on the PT -all elements in the same group have the same number of valence electrons

average atomic mass

weighted average of all the diff. versions of an element -closet to the most common isotope of an element