Chapter 3 Matter—Properties and Changes (Ruiki Basilio, Angeles Phan, Albert Alavarez and Carlos Quintanilla)
3.1 Properties of Matter
· A substance is a form of matter with a uniform and unchanging composition.
· Physical properties can be observed without altering a substance’s composition. Chemical properties describe a substance’s ability to combine with or change into one or more new substances.
· Both physical and chemical properties are affected by external conditions such as temperature and pressure.
· The three common states of matter ate solid, liquid, and gas.
Review Questions:
List three examples of substances. Explain why each is a substance.
Classify each of the following as a physical property or a chemical property.
a. aluminum has a silvery color
b. gold has a density of 19g/cm3
c. sodium ignites when dropped in water
d. water boils are 100°C
e. silver tarnishes
f. mercury is a liquid at room temperature
3.2 Changes in Matter
· A physical change alters the physical properties of a substance without changing its composition.
· A chemical change, also known as a chemical reaction, involves a change in a substance’s composition.
· In a chemical reaction, reactants form products.
· The law of conservation of mass states that mass sis neither created nor destroyed during a chemical reaction; it is conserved.
Review Questions:
Describe the difference between a chemical change and a physical change.
Classify each of the following as a physical change or a chemical change.
a. Breaking a pencil in two
b. Water freezing and forming ice
c. Frying an egg
d. Burning wood
e. Leaves turning color in the fall
3.3 Mixtures of Matter
· A mixture is a physical blend of two or more pure substances in any proportion.
· Solutions are homogenous mixtures.
· Mixtures can be separated by physical means. Common separation techniques include filtration, distillation, crystallization, and chromatography.
Review Questions:
Describe how a homogeneous mixture differs from a heterogeneous mixture.
Describe a method that could be used to separate each of the following mixtures.
a. Iron filings and sand
b. Sand and salt
c. The components of ink
d. Helium and oxygen gases
3.4 Elements and Compounds
· Elements are substances that cannot be broken down into simpler substances by chemical or physical means.
· The elements are organized in the periodic table of elements.
· A compound is a chemical combination of two or more elements. Properties of compounds differ from the properties of their component elements.
· The law of definite proportion states that a compound is always composed of the same element in the same proportions.
· The law of multiple proportions states that if elements form more than one compound, those compounds will have compositions that are small, whole-number multiples of each other.
Review Questions:
Is it possible to distinguish between an element and a compound? Explain.
Name the elements contained in the following compounds.
a. Sodium chloride (NaCl)
b. Ammonia (NH3)
c. Ethanol (C2H6O)
d. Bromine (Br2)
Chapter 4 The Structure of the Atom (Gonzalez Ileana & Barrios Cindy)
4.1 Early Theories of Matter
· The Greek philosopher Democritus was the first person to propose the existence of atoms.
· In 1808, Dalton proposed his atomic theory, which was based on numerous scientific experiments.
· All matter is composed of atoms. An atom is the smallest particle of an element that maintains the properties of that element. Atoms of one element are different from atoms of other elements.
4.2 Subatomic Particles and the Nuclear Atom
· Atoms are composed or negatively charged electrons, neutral neutrons, and positively charged protons. Electrons have a 1 – charge, protons have a 1+ charge, and neutrons have no charge. Both protons and neutrons have masses approximately 1840 times that of an electron.
· The nucleus of an atom contains all of its positive charge and nearly all of its mass.
· The nucleus occupies an extremely small volume of space at the center of an atom. Most of an atom consists of empty space surrounding the nucleus through which the electrons move.
· Atomic Number = number of protons; number of protons = number of electrons
· Mass number - Atomic number = number of neutrons (mass number is also known as atomic mass)
Review Questions:
1. An atom is composed mainly of:
A) Protons
B) Electrons
C) Empty Space
D) Water
2. True or False
The smallest particle of an element that retains the properties of the element is called an atom
3. Electrons are located in
A) The nucleus
B) The space surrounding the nucleus
C) The space surrounding the atom
D) In the nucleolus
4. The negatively charged particles are called?
A) Neutrons
B) Protons
C) Electrons
D) Isotopes
Answer Key: C, True, B , C
4.3 How Atoms Differ
· The number of protons in an atom uniquely identifies an atom. This number of protons is the atomic number of the atom.
· Atoms have equal numbers of protons and electrons, and thus, no overall electrical charge.
· An atom’s mass number (or atomic mass) is equal to its total number of protons and neutrons.
· Atoms of the same element with different numbers of neutrons and different masses are called isotopes.
· The atomic mass of an element is a weighted average of the masses of all the naturally occurring isotopes of that element.
4.4 Unstable Nuclei and Radioactive Decay
· Chemical reactions involve changes in the electrons surrounding an atom. Nuclear reactions involve changes in the nucleus of an atom.
· The neutron-to-proton ratio of an atom’s nucleus determines its stability. Unstable nuclei undergo radioactive decay, emitting radiation in the process.
Chapter 5 Electrons in Atoms (Aukura Williams, Valerie Zuniga, Jacqueline Rodriguez)
5.1 Light and Quantized Energy
· All waves can be described by their wavelength, frequency, amplitude. and speed.
· Light is an electromagnetic wave. In a vacuum all electromagnetic waves travel at the speed of 3.00 x 108 m/s.
· All electromagnetic waves may be described as both waves and particles. Particles of light are called photons.
· Energy is emitted and absorbed by matter in quanta.
· In contrast the continuous spectrum produced by white light, an element’s atomic emission spectrum consists of a series of fine lines of individual colors.
5.2 Quantum Theory and the Atom
· According to the Bohr model of the atom, hydrogen’s atomic emission spectrum results from electrons dropping from higher-energy atomic orbits to lower-energy atomic orbits.
· The de Broglie equation predicts that all moving particles have wave characteristics and relates each particle’s wave length to its mass, its velocity, and Planck’s constant.
· The quantum mechanical model of the atom is based on the assumption that electrons are waves.
· The Heisenberg uncertainty principle states that it is not possible to know precisely the velocity and the position of a particle at the same time.
· Electrons occupy three-dimensional regions of space called atomic orbitals. There are four types of orbitals, denoted by the letters s, p, d, and f.
Review Questions:
1. What is the complete electron configuration of a scandium atom?
A. 1s22s22p63s23p64s23d1
B. 1s22s22p73s23p74s23d1
C. 1s22s22p53s23p54s23d1
D. 1s22s12p73s13p74s23d1
5.3 Electrons Configurations
· The arrangement of electrons in an atom is called the atom’s electron configuration. Electron configurations are prescribed by three rules: the aufbau principle, the Pauli exclusion principle, and Hund’s rule.
· Electrons related to the atom’s highest principle energy level are referred to as the valence electrons. Valence electrons determine the chemical properties of an element.
· Electron configurations may be represented using orbital diagrams, electron configuration notation, and electron-dot structures.
Review Questions:
1. Which of the following orbitals has the highest energy?
A. 4f
B. 5p
C. 6s
D. 3d
Chapter 6 The Periodic Table and Periodic Law (Christopher Molina and Fortunato Rojas)
6.1 Development of the Modern Periodic Table
· Period law states that when the elements are arranged by increasing atomic number, there is a periodic repetition of their chemical and physical properties.
· Newland’s law of octaves, which was never accepted by fellow scientists, organized the elements by increasing atomic mass. Mendeleev’s periodic table, which also organized elements by increasing atomic mass, became the first widely accepted organization scheme for the elements. Moseley fixed the errors inherent in Mendeleev’s table by organizing the elements by increasing atomic number.
· The periodic table organizes the elements into periodic (rows) and groups (columns) by increasing atomic number. Elements with similar properties are in the same group.
· Elements are classified into metals, nonmetals, or metalloids. The stair-step line on the table separates metals from nonmetals. Metalloids border the stair-step line.
6.2 Classification of the Elements
· Elements in the same group on the periodic table have similar chemical properties because they have the same valence electrons configuration.
· The four blocks on the periodic table can be characterized as follows:
§ S-block: filled or partially filled s orbitals
§ P-blocks: filled or partially filled p orbitals
§ D-block: filled outer most s orbital of energy level n and filled or partially filled d orbitals of energy level n – 1.
§ F-block: filled outermost s orbital, and filled or partially filled 4f and 5f orbitals.
· For the group and elements, an atom’s group number equals its number of valence electron.
· The energy level of an atom’s valence electrons equals its period number.
· The s2p6 electron configuration of the group 8A elements (noble gases) is exceptionally stable.
6.3 Periodic Trends
· Atomic radii generally decrease as you move left to right across a period and increase as you move down a group.
· Positive ions are smaller than the neutral atoms from which they form. Negative ions are larger than the neutral atoms from which they form.
· Ionic radii of both positive and negative ions decrease as you move left to right across the period. Ionic radii of both positive and negative ions increase as you move down a group.
· Ionization energy indicates how strongly an atom holds onto its electrons. After the valence electrons have been removed from an atom, there is a tremendous in the ionization energy required to remove the next electron.
· Ionization energies generally increase as you move left to right across a period and decrease as you move down a group.
· The octet rule states that atoms gain, lose, or share electrons in order to acquire the stable electron configuration of a noble gas.
· Electronegativity, which indicates the ability of atoms of an element to attract electrons in a chemical bond, plays a role in determining the type of bond formed between elements in a compound.
· Electronegativity values range from 0.7 to 3.96, and generally increase as you move left to right across a period and decrease as you move down a group.
Review Questions:
1. What are groups and periods and how are they different?
Answer: Groups are the columns in the periodic table and periods are the rows which is their difference.
2. Where are alkali metals and alkaline earth metals located in the periodic table?
Answer: Alkali metals are located in the first group and alkaline earth metals are located in the second group.
3. What are valence electrons?
Answer: These are the electrons in the outermost energy level.
4. Give the electron configuration of Al.
Answer: 1s22s22p63s23P1
5. What does ionization energy and atomic radius have in common?
Answer: Their similarity is that they both decrease left to right across the period.
6. What does it mean for an electron to have a high electronegativity?
Answer: It means that it is able to attract any electrons to them when they bond with another atom.
Chapter 7 The Elements (Marlin Gramajo & Jazmine Gomez)
7.1 Properties of S-block Elements
· The number and location of valence electrons determine an elements precision on the periodic table and its chemistry.
· Properties within a group are not identical because members have different numbers of inner electrons.
· Similarities between period two elements and period three elements in neighboring groups are called diagonal relationships.
· The representative elements in groups 1A through 8A have only S and P electrons.
· Because hydrogen has a single electron, it can behave as a metal and loose an electron or behave as a nonmetal and gain an electron,
· The alkali and earth metals in group 1A and 2A are the most reactant metals.
· Metals form mixtures called alloys whose composition can be adjusted to produce different properties.
· Sodium and Potassium are the most abundant alkali metals. Many biological functions are controlled by Sodium and Potassium ions.
· Calcium is essential for healthy teeth and bones. It is most often found as Calcium carbonate, which can decompose to form lime-one of the most important industrial compounds.
· Magnesium is used in lightweight, yet strong alloys. Magnesium ions are essential for metabolism, muscle function and photosynthesis.
Review Questions:
1. What are Group 1A elements called?
A) Alkali metals*
B) Halogens
C) Alkaline
D) Alkaline Earth metals
2. What are the most abundant alkali metals?
A) francium
B) nitrogen
C) sodium and potassium*
D) calcium
7.2 Properties of P-block elements
· P-block elements include elements, metalloids, nonmetals, and inert gases.
· Aluminum is the most abundant metal in Earth’s crust. Much more energy is needed to extract Aluminum from its ore to recycle aluminum.
· Because of carbon atom can join with up to four other carbon atoms, carbon forms millions of organic compounds.
· Graphite and diamonds are allotropes of carbon.
· The most abundant element in Earth’s crust, silicon and oxygen, are usually found in silica , which can be melted and rapidly cooled to form glass.
· Lead, which is still used in storage batteries, was used in pipes, paint, and gasoline until people realized the danger of lead poisoning.