General Chemistry Chapter 2

Chapter 2 Lecture Outline

• This is a lecture outline for a General, Organic, and Biological Chemistry course.
• The outline was prepared by Jan Henri G. Carpizo, RMT of the University of Pangasinan, and is from the second edition of the textbook.
• The textbook is published by The McGraw-Hill Companies.

2.1 Elements

• An element is a pure substance that cannot be broken down into simpler substances by a chemical reaction.
• Each element is represented by a one- or two-letter symbol.
• Elements are organized in the periodic table.
• The position of an element in the periodic table reveals information about its chemical properties.
• Elements in the periodic table are categorized into metals, nonmetals, and metalloids.
• Metals are located on the left side of the periodic table, are good conductors of heat and electricity, and are generally shiny solids at room temperature (except for mercury, which is a liquid).
• Nonmetals are located on the right side of the periodic table, are generally poor conductors of heat and electricity, and can exist as solids, liquids, or gases at room temperature.
• Metalloids have properties that are intermediate between metals and nonmetals. Metalloids are found along a dividing line on the periodic table.
• The essential elements for life are listed.
• Building-block elements are the most abundant in human bodies (Oxygen, Carbon, Hydrogen, Nitrogen).
• Trace elements are present in lesser quantities and are still vital for bodily functions.

Activity (Page 9)

• This activity directs students to locate elements on the periodic table and classify them as metals, nonmetals, or metalloids.
• The activity provides a list of elements for classification (Titanium, Chlorine, Krypton, Palladium, Arsenic, Cesium, Selenium, Osmium)

2.2 Structure of the Atom

• All matter is composed of building blocks called atoms.
• Atoms are composed of subatomic particles: protons, neutrons, and electrons.
• Protons are positively charged, neutrons are neutrally charged, and electrons are negatively charged.
• Protons and neutrons are located in the nucleus. Electrons orbit the nucleus.
• The mass of a proton is roughly 1 amu, and the mass of a neutron is roughly 1 amu. The mass of an electron is negligible.
• The position of an element in the periodic table gives the atomic number (equal to the number of protons and electrons in a neutral atom).
• Isotopes are atoms of the same element but with a different number of neutrons.

2.3 Isotopes

• Isotopes are atoms with the same number of protons (and electrons if neutral) but differing neutron counts.
• The mass number (A) defines the sum of protons and neutrons.
• Atomic weight is a weighted average of naturally occurring isotopes.
• Students should know how to calculate atomic weight
• Activity (Page 18): Calculate numbers of protons , neutrons, and electrons in an atomic example.

Activity (Page 19)

• This activity prompts students to determine several different atomic properties like atomic number, mass number, amounts of protons, neutrons and electrons from given examples.

2.3 Isotopes, B. Atomic Weight

• Atomic weight is the weighted average of the masses of naturally occurring isotopes of an element.
• Atomic weight is expressed as a numerical value.
• This activity includes a guided example for determining chlorine's atomic weight.

2.4 The Periodic Table

• A row in the periodic table is called a period.
• A column in the periodic table is called a group.
• Elements in the same group have similar chemical properties.
• Elements in the main groups (1A-8A) have properties based on their position in the table. Transition metals are a separate group in the middle, with their own properties.

2.4 The Periodic Table, B-1 Characteristics of Groups 1A and 2A

• Alkali metals (group 1A) and alkaline earth elements (group 2A) display similar properties.
• These elements share properties such as softness and luster, low melting points, being good conductors of heat and electricity. They also react with water to produce basic solutions.

2.4 The Periodic Table, B-2 Characteristics of Groups 7A and 8A

• Halogens (group 7A) are highly reactive elements that exist as pairs.
• Noble gases (group 8A) are unreactive elements that are usually found in single form.

2.4 The Periodic Table, C. The Unusual Nature of Carbon

• Carbon has an unusual capability to form bonds with itself and other elements.
• Some of the elemental forms of carbon include diamond and graphite.

2.5 Electronic Structure

• Electrons occupy specific regions around the nucleus called orbitals, which have associated energies.
• Shells are energy levels containing orbitals.
• The number of electrons that can be contained within each shell follows patterns.

2.5 Electronic Structure

• Shells are divided into subshells. Subshells are labeled.
• Orbitals are regions within subshells where there is a high probability of finding electrons. Each orbital can only hold two electrons.
• There is a pattern of the number of electrons each orbital can contain.

2.6 Electron Configuration

• Electron configuration describes the arrangement of electrons in an atom's energy levels and subshells.
• Electrons fill orbitals in order of increasing energy.
• Each orbital holds a maximum of 2 electrons.
• When energy levels are equal, electrons occupy orbitals one at a time until each orbital is half filled before being completely filled.
• Orbital diagrams use boxes and arrows to represent electrons and their placements.

2.6 Electron Configuration, A. First-Row Elements (Period 1)

• For the elements hydrogen (H) and helium (He), orbital notation is illustrated.

2.6 Electron Configuration, B. Second-Row Elements (Period 2)

• For the elements lithium, carbon and Neon, orbital notation is illustrated.

2.6 Electron Configuration, C. Other Elements

• Illustrative examples are shown for Calcium.

2.7 Valence Electrons

• Valence electrons are electrons in the outermost shell (valence shell) of an atom.
• The number of valence electrons determines the chemical properties of an atom.
• Valence shell = largest value of "n".
• Elements in the same group have the same number of valence electrons, and they tend to share similar chemical properties.

2.7 Valence Electrons, A. Relating Valence Electrons to Group Number

• Group number (1A-8A = # of valence electrons). This is true for most groups (with exception of He).

2.7 Valence Electrons, B. Electron-Dot Symbols

• Electron-dot symbols are used to represent valence electrons.
• Dots are placed around the chemical symbol to indicate the number of valence electrons.

2.8 Periodic Trends, A. Atomic Size

• Atomic size increases as you move down a column on the periodic table.
• Atomic size decreases as you move across a period going from left to right on the periodic table

2.8 Periodic Trends, B. Ionization Energy

• Ionization energy is the energy needed to remove an electron from a neutral atom.
• Ionization energy increases as you move across a period. Ionization energy decreases as you move down a column.

This quiz is based on Chapter 2 of the General, Organic, and Biological Chemistry course. It covers the fundamentals of elements, their classification, and properties as highlighted in the lecture outline by Jan Henri G. Carpizo. Test your understanding of how elements are structured within the periodic table.