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Chapter 3 Elements and the Periodic Table

Chapter 3 Elements and the Periodic Table. I. Intro to Atoms A. Structure – atoms made of small particles 1.Particles in atoms A. Nucleus - center of atom B. Proton – positive charge - in nuc . C. Neutron – no charge – in nuc . D. Electron – negative charge – outside the nucleus

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Chapter 3 Elements and the Periodic Table

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  1. Chapter 3 Elements and the Periodic Table • I. Intro to Atoms • A. Structure – atoms made of small particles • 1.Particles in atoms • A. Nucleus - center of atom • B. Proton – positive charge - in nuc. • C. Neutron – no charge – in nuc. • D. Electron – negative charge – outside the nucleus • E. Number of protons & electrons is the same. Balance charge. • 2. Cloud of Electrons a. Electrons move around the nucleus, those with the most energy are furthest away, those with less are closest to nuc. b. Most of the atom’s volume is the space where electrons move. • 3. Comparing Particle Masses • Electrons account for most of atom’s volume, but hardly any mass • It takes 2000 electrons to equal the mass of 1 proton. Protons and neutrons are about = c. Scientists use units called amu’s (atomic mass units) to measure mass of atom. Electrons have 1/2000 amu, protons and neutrons are about 1 amu

  2. Keep writing. . .. • B. Atoms and Elements • 1. an element can be identified by the number of protons in the nucleus. • 2. Atomic number – every atom of an element has the same number of protons. The atomic number is the number of PROTONS in the nuc. • 3. Isotopes – Atoms with the same number of protons but a different number of neutrons. • 4. carbon has 3 isotopes (Carbon 12, Carbon 13,and Carbon 14) • 5. Isotopes can be identified by MASS number – which is the sum of protons and neutrons. So, if carbon has atomic number 6 and each proton and neutron = 1 amu, the atomic mass should be 12, but if it’s more . Then it is because it must be found in other forms where the neutron count is higher.

  3. Last part of Section 1 • C. Modeling Atoms • 1. a sheet of paper is 10,000 atoms thick. . Hard to imagine so we use models to help us. • 2. Could be diagram, or object to help visualize what an atom looks like • 3. Modern model explains why most elements react with other elements , while few hardly react at all!

  4. II. Organizing Elements • A. Patterns • 1. Mendeleev knew about similar prop. • 2. He put phys. char. On cards • 3. noted a pattern when arranged by atomic mass. Noticed properties repeated – group • 4. didn’t always work so inferred that some had not yet been discovered. • 5. Today arrang by atomic number, and properties repeat in each period (row)

  5. There’s more • B. Finding Data on Elements • 1. atomic number - # of protons • 2. Chemical symbol – abbrev. For name. 1 or 2 letters (Latin names) • 3. Average Atomic mass . .comb. Percent. Of all the isotopes

  6. Last one • C. Organizing • 1. Properties of element can be predicted by looking at where it is on the periodic table. • 2. Periods – horizontal rows • 3. Groups – vertical columns known as families. The elements in group 1 are all metals that react violently in water.

  7. Go to this website, read and try! • http://misterguch.brinkster.net/eqnbalance.html

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