Chapter 1: Atoms
Law of Conservation of Mass
Matter is not created nor destroyed in any chemical or physical change
Hg
Mercury
Theory example
Newton's theory of gravitation explains why objects tend to fall toward the Earth.
Theory, law or observation? When a match burns, heat is evolved.
Observation
Theory, law or observation? When iron rusts in a closed container, the mass of the container and its contents does not change.
Observation
What distinguishes a mixture of hydrogen and oxygen from a sample of water?
One is a pure substance, compound, one is a mixture
isotopes
One of two or more atoms of the same element with the same number of protons but different numbers of neutrons and consequently different masses.
scientific law example
Over the years people observed that every morning the sun rises in the east, and every night the sun sets in the west. These observations can be described in a law stating, "The sun always rises in the east and sets in the west."
Bohrs
Planetary model, flawed but was the closest
Properties of electrical charge
Positive and negative electrical charges attract each other. Positive charges repel positive charges. Negative charges repel negative charges. Positive and negative charges of exactly the same magnitude sum to zero when combined.
Dalton
Proposed the plum-pudding model. First complete attempt to describe all life in terms of particles. Based his theory on the Law of Conservation of Mass and Law of Definite Proportions.
Proust
Published the Law of Definite Proportions. This law states that a compound is composed of exact proportions of elements by mass regardless of how the compound was created.
Mixture or Pure Substance? Aluminum. Carbon Dioxide. Vegetable soup. Sweat.
Pure substances: aluminum (element) and carbon dioxide(compound). Mixtures: Vegetable soup (heterogenous) and sweat (homogenous)
composition of matter
Refers to the type of particles that compose matter;
atomic mass
The average mass in amu of the atoms of a particular element based on the relative abundance of the various isotopes; numerically equivalent to the mass in grams of one mole of the element.
What information about atomic structure was determined by Milkians oil drop experiment?
The charge of an electron
radioactivity
The emission of subatomic particles or high-energy electromagnetic radiation by the unstable nuclei of certain atoms
electrostatic forces
The forces of attraction and repulsion between electrically charged particles.
Which statement best captures one of the differences between the law of definite proportions and the law of multiple proportions?
The law of definite proportions applies to two or more samples of the same compound while the law of multiple proportions applies to two different compounds containing the same two elements (A and B).
law of definite proportions
The law stating that all samples of a given compound have the same proportions of their constituent elements.
When a log completely burns in a campfire, the mass of the ash is much less than the mass of the log. What happens to the matter that composed the log?
The matter that composed the log reacts to form gases that are released into the air. Most of the matter that composed the log reacts with oxygen molecules in the air. The products of the reaction (mostly carbon dioxide and water) are released as gases into the air.
Avagadro's number
The number of C 12 atoms is exactly 12 g of C 12; equal to 6.02214 × 10²³. Typically rounded to 6.022 × 10²³ particles
atomic number (Z)
The number of protons in an atom; the atomic number defines the element
natural abundance
The relative percentage of a particular isotope in a naturally occurring sample with respect to other isotopes of the same element.
solid
The state of matter in which atoms or molecules are packed close to one another in fixed locations with definite volume
gas
The state of matter in which atoms or molecules have a great deal of space between them and are free to move relative to one another; lacking a definite shape or volume, a gas conforms to the shape and volume of its container
liquid
The state of matter in which atoms or molecules pack about as closely as they do in solid matter but are free to move relative to each other, resulting in a fixed volume but not a fixed shape.
mass number A
The sum of the number of protons and neutrons in an atom.
nuclear theory
The theory that most of the atom's mass and all of its positive charge are contained in a small, dense nucleus.
Theory, law or observation? All matter is made of tiny, indestructible particles called atoms.?
Theory
How to separate mixtures
They can be separated into their component parts through physical means
How to seperate pure chemical substances
They require chemical or nuclear reactions to separate them
Sn
Tin
Law of Multiple Proportions
When two elements (call them A and B) form two different compounds, the masses of element B that combine with 1 g of element A can be expressed as a ratio of small whole numbers.
Isotope notation
X- A Example: Ne-20 Ne-21 Ne-22
electric field
a field of force surrounding a charged particle
homogeneous mixture (solution)
a mixture that is uniform in its properties throughout. An example is tea with sugar, two types of particles that are thoroughly mixed.
Hypothesis
a tentative explanation of the observations. The hypothesis is not necessarily correct but it puts the scientist's understanding of the observations into a form that can be tested through experimentation.
Scientific law
a verbal or mathematical generalization of a phenomenon that describes past observations and can be used to predict future observations.
mass spectrometry
an experimental method of determining the mass and relative abundance of isotopes in a given sample using an instrument called a mass spectrometer
mass of a proton and neutron
approx 1 amu
Quantitative observations
are measurements consisting of both numbers and units, such as the observation that ice melts at 0∘C .
Qualitative observations
are observations that do not rely on numbers or units, such as the observation that water is clear.
Expierments
are performed to test the validity of the hypothesis. They are controlled procedures preferably made under conditions in which the variable of interest is clearly distinguishable from any others, that are used to generate observations then used to confirm or refute the hypothesis.
Atoms
are the basic particles that compose ordinary matter. 91 different types of atoms naturally exist.
Cu
copper
observations can be
either quantitative or qualitative.
Pure chemical substances be further divided into _______ or _______
elements or compounds.
Most of the volume of the atom is _______, throughout which tiny, negatively charged electrons are dispersed
empty space
A good hypothesis is
falsifiable and testable
How many atoms are in 2.16 g Hg? Steps.
g Hg → mol Hg → atoms of Hg. Remember conversion factors. Give * 1 mol hg / atomic mass of Hg * Avagadro's number / 1 mol hg
Au
gold
Mixtures can be either _______ or _______
heterogeneous or homogeneous.
The gain or loss of an electron by an atom will result in a ____
ion.
scientific method
is a procedure used to search for explanations of nature. The scientific method consists of making observations, formulating hypotheses, designing and carrying out experiments, and repeating this cycle.
Pb
lead
A blood sample contains several different types of cells, each of which contains different combinations of specific ions and molecules. The cells are suspended in water, and the water also contains many molecules and ions. Which term or terms could be used to describe this sample of blood?
mixture, heterogeneous
A sample of tap water consists of water, fluoride ions, calcium ions, and several other dissolved ions. The ions are evenly distributed throughout the water. Which term or terms could be used to describe this sample of tap water?
mixture, solution, homogeneous mixture
There are as many _____charged electrons outside the nucleus as there are _____ charged particles within the nucleus, so that the atom is electrically neutral
negatively; positively
atoms are electrically
neutral
Most of the atom's mass and all of its positive charge are contained in a small core called the
nucleus
matter is composed of
particles
K
potassium
The structure of these particles determines the _____ of matter
properties
The number of ______ defines the element
protons
Which subatomic particles are found in the nucleus of the atom?
protons and neutrons
A balloon is filled with pure carbon dioxide. Which term or terms could be used to describe the contents of this balloon?
pure chemical substance, compound. All compounds are pure. If this sample of carbon dioxide (CO2) had been impure, we would call it a mixture, not a compound.
A filament of a light bulb is made from a pure sample of tungsten. Which term or terms could be used to describe this sample of tungsten?
pure chemical substance; element. All elements are pure. If this sample of tungsten had been impure, we would call it a mixture, not an element.
All substances are either _____ or ____
pure chemical substances or mixtures
Compound example
pure substances that can be broken down into simpler, stable substances An example is water.
Element example.
pure substances that cannot be broken down into simpler, stable substances and is made of one type of atom. An example is carbon
Ag
silver
Na
sodium
state of matter
solid, liquid, gas
Homogeneous mixtures are also called
solutions
The Law of Conservation of Mass states that in a chemical equation
the number of atoms of the reactants is the same as the number of atoms of the products
chemistry
the science that seeks to understand the behavior of matter by studying the behavior of atoms and molecules
The mass number of an element is equal to
the sum of the number of protons and the number of neutrons
W
tungsten
The particles that compose water are
water molecules
Atomic mass equation
Σn(fraction of isotope n)×(mass of isotope n).
fundamental charge of a single electron
-1.60 x 10⁻¹⁹ C
mass of an electron
.00055 amu
A water molecule is composed of three atoms:
1 oxygen, 2 hydrogen
charge to mass ratio of electron
1.76 x 10⁸ Coulombs/g
The atomic number of carbon is 6. What is the mass number of a carbon atom with 5 neutrons?
11
An atom has a mass number of 27 and 14 neutrons. What is the atomic number of this atom?
13
An atom of calcium is represented by ⁴²₂₀ Ca. How many neutrons are in the nucleus of this atom?
22
Suppose that one of Millikans oil drops has a charge of -4.8 × 10-19 C. How many excess electrons does the drop contain?
3, because the charge of a single electron is -1.60 x 10⁻¹⁹ C. This sample has 3 electrons based on the charge.
A compound containing only carbon and hydrogen has a carbon-to-hydrogen mass ratio of 11.89. Which carbon-to-hydrogen mass ratio is possible for another compound composed only of carbon and hydrogen? 4.66 3.97 7.89 2.50
3.97. Divide the mass ratio with one of the options, it should be a small whole number. 11.89 / 3.97 = 2.99 or 3
How many Neutrons are in 1000 atoms of Cl-37? Cl's atomic # is 17
37 is the mass number. 17 is the number of protons. In a single atom there are 20 neutrons. So in 1000, there are 20,000
electrical charge
A fundamental property of certain particles that causes them to experience a force in the presence of electric fields.
Theory
A hypothesis that has been tested with a significant amount of data. It is a model that can be used to explain not only what occurs in nature, but why it occurs.
Which statement best explains the difference between a law and a theory?
A law summarizes a series of related observations, whereas a theory gives the underlying reasons for them.
Heterogeneous mixture example
A mixture that is not uniform throughout. Wet sand has two types of particles that separate in distinct regions.
Anions
A negatively charged ion, having gained electrons. Written such as F⁻.
electron
A negatively charged, low-mass particle found outside the nucleus of all atoms that occupies most of the atom's volume but contributes almost none of its mass
cathode ray tube
A partially evacuated tube equipped with electrodes to produce cathode rays
cations
A positively charged ion, having lost electrons. Written such as Li⁺.
protons
A positively charged subatomic particle found in the nucleus of an atom.
Chemical reaction
A process by which one or more substances are converted to one or more different substances; see also chemical change
substance
A specific instance of matter such as air, water, or sand.
cathode rays
A stream of electrons produced when a high electrical voltage is applied between two electrodes within a partially evacuated tube.
pure substance
A substance composed of only one type of atom or molecule. Its composition is invariant.
Mixture
A substance composed of two or more different types of atoms or molecules that can be combined in variable proportions
compound
A substance composed of two or more elements in fixed, definite proportions.
element
A substance that cannot be chemically broken down into simpler substances
mole
A unit defined as the amount of material containing 6.02214 × 10²³ particles
atomic mass unit
A unit used to express the masses of atoms and subatomic particles; defined as 1/12 the mass of a carbon atom containing 6 protons and 6 neutrons.
ion
An atom or molecule with a net charge caused by the gain or loss of electrons
Nuetrons
An electrically neutral subatomic particle found in the nucleus of an atom, with a mass almost equal to that of a proton.
Sb
Antimony
Matter
Anything that has mass and takes up space. It is particulate - it is composed of particles.
Which concept was demonstrated by Rutherford's gold foil experiment?
Atoms are mostly empty space. In Rutherford's gold foil experiment, most of the particles passed through the foil, indicating that most of the atom is empty space.
How to answer: Which sample contains the greatest number of atoms?
Compare the molar masses and the grams provided. Example 14 g of Carbon. C has a molar mass of 12.01 or 1 mol. This sample is slightly larger than 1 mol of Carbon. The larger the amount of mol, the more atoms present in the sample.
Heisenberg
Concluded that it is impossible to know moment of electrons. Developed quantum theory and the cloud model
A solid copper cube contains 4.3 × 1023 atoms. What is the edge length of the cube? The density of copper is 8.96 g/cm3.
Convert atoms → mol → g → cm³
J. J Thompson
Discovered the existence of electrons with the cathode ray/tube
Atomic Theory (John Dalton)
Each element is composed of tiny, indestructible particles called atoms. All atoms of a given element have the same mass and other properties that distinguish them from the atoms of other elements. Atoms combine in simple, whole-number ratios to form compounds. Atoms of one element cannot change into atoms of another element. In a chemical reaction, atoms only change the way that they are bound together with other atoms.
Neutral fluorine F atoms contain 9 protons and 9 electrons. What happens with F gains an electron?
F + 1e⁻ → F⁻. Gaining an electron creates a negatively charged element.
Determine the number of atoms in 1.85 mL of mercury. The density of mercury is 13.5 g/mL.
Given mL→ density of mercury → mols → atoms
Rutherford experiment conclusions
Gold foil experiment. Concluded that tiny, dense nucleus was the reason particles deflected.
molecules
Groups of two or more atoms held together by chemical bonds
Classify: Bacon Strip
Heterogenous Mixture
Classify: Potato Chips
Heterogenous Mixture
Classify: Freshly opened can of soda
Heterogenous mixture
Classify: Gasoline
Homogenous Mixture
Classify: A solid gold bar
Homogenous mixture
Is density intensive or extensive.
Intensive.
Fe
Iron
Theory, law or observation? In chemical reactions, matter is neither created nor destroyed
Law
Neutral lithium Li atoms contain 3 protons and 3 electrons. What happens with Li loses an electron?
Li→ Li ⁺ + 1e⁻. When an electron is lost, the element becomes positively charged