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Honors Chemistry: Chapter 2
Terms in this set (75)
The 3 subatomic particles
1. Proton (+ charge)
2. Neutron (no charge)
3. Electron (- charge)
Atoms have equal numbers of what?
Protons and electrons so there's a net charge of 0
The 4 basic forces in nature
3. Strong Nuclear
4. Weak Nuclear
= An attractive force between all objects in proportion to their mass
- Very small in atoms so there's minimal significance in chemistry
= An attractive or repulsive force (like charges repel and unlike attract) between electrically charged particles
- Fundamental to understanding chemical behavior of atoms
Strong Nuclear Force
= Act between subatomic particles in nucleus
- Stronger than electrical forces repelling so nuclei don't explode
Weak Nuclear Force
- Fall between electromagnetic and gravitational in strength
- Radioactivity gives evidence that these forces exist
The 4 forces ranked from strongest-->weakest
1. Strong Nuclear
3. Weak Nuclear
= 1 x 10^-10 m
Which part of the atom plays a major role in chemical reactions?
What distinguishes one atom from another?
The number of protons in the nucleus
Atomic mass, A
= The number of protons + the number of neutrons
Atomic number, Z
= Number of protons
= An atom with the same number of protons but varying numbers of neutrons and therefore varying atomic mass numbers
-Have identical chemical properties but differing physical properties
John Dalton (1803-1807)
Created the current atomic theory:
1. Each element is composed of extremely small particles called atoms
2. All atoms of a give element are identical; the atoms of different elements are different and have different properties (including mass)
3. Atoms of an element are not changed into different types of atoms by chemical reactions; atoms are neither created nor destroyed in chemical reactions
4. Compounds are formed when atoms of more than one element combine; a given compound always has the same relative # and kind of atoms
- Also created the Laws of Definite Proportions, Conservation of Matter, and Multiple Proportions
Law of Constant Composition / Definite Proportions
= In a given compound, the #'s and types of atoms are constant
Law of Conservation of Matter
= The total mass before the reaction = the total mass after the reaction
- AKA matter cannot be created nor destroyed
Law of Multiple Proportions
= In a family of compounds made from the same two elements (ex: CO, CO2), the masses of element "B" that can combine with a fixed mass of element "A" are in small, whole number ratios
- A and B are elements
J.J. Thompson (1897)
- Cathode ray experiment
- Found the ratio of an electron charge to the mass of an electron
- 1.76 x 10^8 C/g
- Plum pudding model
Robert Millikan (1909)
- Oil drop experiment
- Measured the charge of a single electron and therefore using Thompson's ratio could find the mass of a single electron
- Mass: 9.10939 x 10^-28 g
- Charge: 1.60 x 10^-19 C
Ernest Rutherford (1911)
- Gold foil experiment
- Sent positively charged particles through a sheet of gold foil and some were bent, some went straight through, and a few bounced back
- Came up with the planetary model of the atom
- Nucleus was the concentrated mass of positive charge
- Discovered protons in 1919
- Discovered neutrons
- Believed that electrons existed at "quantum" energy levels and that they move in spherical orbits around the nucleus
- There are different levels / orbits based on the different energy levels
- Based on hydrogen light spectra lines
- Charge density cloud model
- Used mathematical probability to predict the position of an electron in the atom at any point in time
- Shapes are normally circular
= Used to calculate how often an isotope of an atom naturally occurs
= The emission of particles and/or particles due to spontaneous radioactive decay of a single atom, fission, or fusion
= Splitting one large atom into two smaller nuclei (sometimes done by neutron bombardment)
= The joining of two lighter nuclei to form one heavier substance
The three main types of radioactive particles:
1. Alpha particles (⍶)
2. Beta particles (β)
3. Gamma rays (Ɣ)
Gamma rays can only be stopped by what?
A lead block
Alpha particles can be stopped by what?
A piece of paper or your skin
Beta particles can be stopped by what?
A piece of wood
Two good uses of radioactivity:
1. Treating / killing of cancer cells in patients
2. Clean, efficient power source (Nuclear power plant)
How are elements arranged in the periodic table?
In order of increasing atomic numbers
Horizontal rows are called what?
Vertical columns are called what?
Alkaline earth metals
Vertical groups have similar chemical properties why?
Because of the similar arrangement of electrons on the outer edge of their atoms
= The medals adjacent to the dividing line
- Have properties falling between metals and nonmetals
- Luster (Shiny)
- Good electrical and heat conductivity properties
What is the only metal to be a liquid at room temperature?
- Found in the upper right side of the periodic table
- At room temperature, some are gases, some are liquids, and some are solids
What group are normally found as uncombined elements in nature?
Most matter is composed of what?
Molecules or ions formed from atoms
= An assembly of 2 or more atoms tightly bound together
- It behaves as a single, distinct object
= Compounds composed of molecules
Most molecular compounds are composed of what?
The Diatomic Molecules
H2, O2, N2, F2, Br2, Cl2, I2
= An atom that loses / gains e's and becomes a charged particle
= + charged ion
= - charged ion
Metal atoms tend to do what (with electrons)?
To lose electrons
Nonmetals tend to do what (with electrons)?
To gain electrons
Compare molecular to ionic compounds**
The 3 types of formulas
= Indicates the actual number and types of atoms in the molecules
= Gives only the simplest whole number ratios of the atoms in each molecule
- Only used for ionic compounds
= Shows the order in which atoms are attached within the molecule
- Atoms are represented by chemical symbols and lines are used to represent bonds
Are parent atoms and daughter ions similar?
No. The ions differ greatly because the electron configuration is substantially different from atom to atom and that changes its chemical properties
Noble gases have what kind of electron arrangements?
Why is it only possible to write an empirical formula for an ionic compound?
Because there is not definite proportions / definite molecule to represent; it just exists 3D in a lattice structure
What kind of charge do ionic compounds have?
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