Introduction and Review:
Chapter 1: Matter – Its Properties and Measurement (Review on your own) Chapter 2: Atoms and Atomic Theory Chapter 3: Chemical Compounds
What in the world isn’t Chemistry
• Matter is the physical material of the universe. • On the microscopic level, matter consists of atoms and molecules. • As we know, molecules may consist of the same type of atoms or different types of atoms.
We encounter chemistry in our everyday lives
Lavoisier, 1743-1794 Conservation of Matter - A chemical equation must be balanced for mass.
Dalton (1766 – 1844) Atomic Theory - A chemical equation must have the same number of atoms of the same kind on both sides.
Dalton’s Atomic Theory
All matter is made of small, indestructible particles called “atoms”. All atoms of a given element are identical and atoms differ for different elements. Compounds are formed when atoms of more than one element combine Atoms of different elements combine in simple, whole number ratios (e.g. 1:1 as in AB; or 1:2 as in AB2)
Consequences of Dalton’s Theory
Combinations of elements are in ratios of small whole numbers (molecules)
Carbon monoxide (CO): 1.33 g of oxygen combines with 1.0 g of carbon or O/C = 1.33 Carbon dioxide (CO2): the ratio of O/C is 2.667 2.667/1.33 = 2.0 which is the ratio of oxygen in CO2/oxygen in CO
What are Atoms?
Atoms are the basic unit of an element that can enter into chemical combination. Dalton – Atoms are small and indivisible – not quite!
Atomic Structure
J.J. Thompson’s Experiment (1898 – 1903) Z/m of the electron = 1.76 × 108 C/g
Milliken’s Oil Drop Experiment (1909) charge of the electron = -1.6022 x 10-19 C Therefore: mass electron = (e- charge)/(e- charge-to-mass ratio) = 9.10 x 10-28 g (9.10939 × 10-28 g)
Atomic Structure
Nuclear Model of the Atom (Rutherford: 1910)
Nucleus • nucleus contains protons and neutrons • nuclear radius is 20,000 times smaller than the atomic radius! (5 cm vs 1 km)
The Modern View of Atomic Structure
The Modern View of Atomic Structure
Particle Proton Neutron Electron
mass 1.67 x 10-24 g 1.67 x 10-24 g 9.11 x 10-28 g
charge 1.60 x 10-19 C No charge -1.60 x 10-19 C
Mass of atom is mostly from nucleus, volume of atom is mostly from electron cloud.
Scale of Atoms
Useful units: 1 u (atomic mass unit) = 1.66054 x 10-24 kg 1 pm (picometer) = 1 x 10-12 m 1 Å (Angstrom) = 1 x 10-10 m = 100 pm = 1 x 108 cm The heaviest atom has a mass of only 4.5 x 10-22 g and a diameter of only 4 x 10-10 m. Typical C-C bond length 1.54 Å (1.5 x 10-10 m)
Isotopes, Atomic Numbers, and Mass Numbers • Atomic number Z = number of protons determines the number of electrons thus the element identity • Atomic Mass - Σ of protons and neutrons • By convention, for element X, we write ZAX. • Isotopes have the same Z but different A (variable number of neutrons) • No two elements have the same value of Z.
Isotopes
1
H 1
Hydrogen
2
H 1
Deuterium
3
H 1
Tritium
How many electrons does each isotope have?
In nature, elements occur as a mixture of isotopes
Atomic Weights
• 1H weighs 1.6735 x 10-24 g and 16O 2.6560 x 10-23 g. • We define: mass of 12C = 12 u. Where 12 u is an exact number (with an infinite number of zeros past the decimal). The mass of every other element in atomic mass units is determined by measuring its mass relative to the mass of 12C. • Using atomic mass units: 1 u = 1.66054 x 10-24 g 1 g = 6.02214 x 1023 u Remember that we must include the isotopes when calculating atomic weights. In nature C: 98.892 % 12C + 1.108 % 13C. • Average mass of C: (0.98892)(12 ) + (0.0108)(13.00335) = 12.011 amu. • What is the mass of a single C atom??
The Periodic Table
• Based on the reactions and properties of the elements and their compounds • Reflects the underlying electronic structure of the elements
(1834 – 1907)
The Periodic Table
• Columns in the periodic table are called groups
Unit 2 Lecture Study Guide 1) What are the parts of an atom? Where are the subatomic particles found? An atom is made up of the central nucleus and the electron cloud. The protons and neutrons are found in the nucleus, while the electrons are in the electron cloud. 2) How does the Atomic Mass # differ from the Atomic #? The atomic mass number is the number of protons and neutrons in the nucleus. Because the neutrons have no charge, they have very little weight. The atomic number is the…
CHAPTER 2 - ATOMS & MOLECULES. In this chapter you will learn about: Symbols and formulas; The Dalton's Atomic Theory; Atomic structure and isotopes; Relative Atomic Masses and average atomic masses; Moles and the Avogadro's number; Molecular and Molar Masses from formulas. ELEMENTS - the fundamental constituent of matter; There are 115 elements known to date and counting, but only 88 are naturally occurring; the rest are synthesized in the particle-accelerators. Eight of those natural elements…
Module 1- Atoms and reactions: Isotopes-are atoms of the same element, with same number of protons and different numbers of neutrons. Atomic (proton) Number- is the number of protons in the nucleus of an atom. Mass (Nucleon) Number- is the number of particles (protons and neutrons) in the nucleus of an atom. An Ion- is a positively charged or negatively charged atom or (covalently bonded) groups of atoms (a molecular ion). Relative Isotopic mass- is the weighted mean mass of an atom of an isotope…
electrically neutral atom is known as the atomic Number. It is usully denoted by A. It is typical number that helps to determine the chemical and physical properties of an atom. In an neutral atom, Atomic Number(A)= Number of electron= Number of the Proton 5. Mass Number Mass number of an atom is the sum of the mass of the sub-atomic particle of an atom, particularly neutron and electron ( the mass of electron is negligible). Thus, mass number is the mass of the nucleus of an atom. It is usually denoted…
Chapter 2 Atoms, Molecules, and Ions Summary of the Chapter • Atomic Structure: protons, electrons and neutrons • The Periodic Table: how is the periodic table organized, metallic and non metallic elements • Molecules and Molecular Compounds: chemical formula • Ions and Ionic Compounds: predicting charges, names and formulas • Binary Molecular Compounds: names and formulas Atomic Theory of Matter A little bit of history: • Democritus (460–370 BC) and other Greek philosophers were the first in…
Atomic Mass Unit 1 Lecture 2 Subatomic Particles Charge (e)* Proton +1 Electron -1 Mass (amu) 1 0.0005 (relatively 0) *Note: The charges are being compared Neutron relative to0each other, they do have 1 specific values (C/g), see Thomson slides Honors… • A neutral atom has an equal amount of protons and electrons • Protons and neutrons have equal masses (they are actually a little bit different, but this is several decimal places out and using a very expensive measuring device • The mass of an…
Assignment Chapter 1 Concept Explorations Key: Concept explorations are comprehensive problems that provide a framework that will enable you to explore and learn many of the critical concepts and ideas in each chapter. If you master the concepts associated with these explorations, you will have a better understanding of many important chemistry ideas and will be more successful in solving all types of chemistry problems. These problems are well suited for group work and for use as in-class activities…
ATOMS AND ELEMENTS Everything is made of atoms Everything is made of tiny lumps of matter called atoms; atoms are made up of even smaller particles. Structure of atoms Protons, electrons and neutrons Electrons are whizzing around the central nucleus. Each electron, and each proton in the nucleus, carries an electrical charge. Electrons carry a negative charge. Protons carry a positive charge. Neutrons have no charge as they are neutral. The electrons have a lot of energy and…
substances that cannot be further simplified. Atoms of the substance all have the same number of protons. Compound: a substance formed when two or more chemical elements are chemically bonded together Atom: The basic unit of a chemical element. Containing protons, neutrons and electrons. Nucleus: The positively charged central core of an atom, containing most of its mass. Contains neutrons and protons. Neutron: A subatomic particle of about the same mass as a proton but without an electric charge…