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Atoms and Elements

Atoms and Elements

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Atoms and Elements

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  1. Atoms and Elements Chapter 4

  2. Dalton’s symbols for elements

  3. Element Names and Symbols • Element Ele • name symbol • 1 or 2 letters (occasionally 3) • 1st letter is capitalized, 2nd letter is lower case.

  4. Distribution of the common elements in nature. 3.2

  5. Elemental Composition of Humans (by mass)

  6. Metallic characters • Metal – shiny, high density, high melting point, great conductor of heat and electricity • Non-metal – dull, low density, low melting point, not good conductor of heat and electricity • Semi-metal – metal-like in appearance and has properties that are between that of a metal and a non-metal.

  7. What are the building blocks of matter? • Early Greeks • Air, Earth, Water, Fire • Democritus (470-370 BC) • Atoms • John Dalton (1766-1844) • Modern Atomic Theory

  8. Dalton’s Atomic Theory • Elements (matter) is composed of small, indivisible particles called atoms. • Atoms of a given element are identical in mass and behavior. • Atoms of different elements differ in mass and behavior. • Chemical combination of elements to make different substances occurs when atoms join together in small whole number ratios. • Chemical reactions only rearrange the way the atoms are combined; the atoms themselves are not changed.

  9. Law of Constant Composition • The law of constant composition states that the composition of a substance is always the same, regardless of how the substance was made or where the substance is found. • For example • All water is 11.3% H and 88.8% O

  10. Law of Multiple Proportions • If the same two elements(A and B) formed two different compounds, there is a whole number relationship between the masses of B in the two different compounds for each gram of A in the compound. • CO 12 g C 16 g O • CO2 12 g C 32 g O

  11. Sub Atomic Particles

  12. Atoms are composed of

  13. Isotopes • Atoms which differ only in the number of neutrons present in the nucleus. • Neutrons help keep the protons together by adding to the strong nuclear force without adding to the mutually repulsive electrical force of the protons. • Generally 1-1.5 neutrons per proton in an atom’s nucleus.

  14. Atomic Number = Z = number of protons in an atom. = number of electrons in a neutral atom. Mass Number = number protons + number neutrons in an atom

  15. Atomic Mass • The average relative mass of the isotopes of an element compared to the atomic mass of carbon-12 (exactly 12 amu) • Atomic mass unit (amu) • 1/12 the mass of a carbon-12 atom • 1.6606 x 10-24 g

  16. Isotopes of Neon

  17. Isotopes of Neon

  18. Chemical Formulas • AxByCz Elemental Symbol Number of atoms