Learning Objectives: The model of atomic theory was 1st proposed by John Dalton

Learning Objectives: The model of atomic theory was 1st proposed by John Dalton www.phwiki.com

Learning Objectives: The model of atomic theory was 1st proposed by John Dalton

Wills, Brad, Meteorologist has reference to this Academic Journal, PHwiki organized this Journal Learning Objectives: The model of atomic theory was 1st proposed by John Dalton in 1803. Atoms are composed of protons, neutrons, in addition to electrons. All atoms of the same element contain the same number of protons ( in addition to electrons) but may vary in the number of neutrons (isotopes). Protons in addition to neutrons are found inside the tiny but dense nucleus, whereas electrons are found in orbitals outside the nucleus. The arrangement of electrons in the orbitals is called the electronic configuration in addition to determines the chemistry of an atom. The different types of atoms are called elements, which are arranged systematically in the periodic table. Having eight valence electrons is particularly desirable (“the octet rule”). The Atomic Theory Dalton’s Atomic Theory All matter is composed of indivisible atoms. All atoms of one element are identical to each other but different than the atoms of other elements. Compounds are as long as med when atoms of different elements combine in whole number ratios. Atoms are rearranged during chemical reactions but atoms cannot be created or destroyed. John Dalton (1766-1844)

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Definitions Law of conservation of matter states that matter is neither lost nor gained during a chemical reaction. Law of definite proportions states that in a compound, the constituent elements are always present in a definite proportion by weight. Structure of the Atom Components Positive protons, negative electrons, in addition to neutral neutrons Atomic Number The number of protons in an atom, which determines what element it is Mass Number Number of protons + the number of neutrons Definitions Protons are positively charged subatomic particles found in the nucleus. Neutrons are electrically neutral subatomic particles found in the nucleus. Electrons are negatively charged subatomic particles found in the space around the nucleus. Nucleus is the small central core of the atom: contains the protons in addition to neutrons.

Separation of alpha, beta, in addition to gamma particles by applying an electric field. Ernest Ruther as long as d (1871-1937) Ruther as long as d’s interpretation of the gold foil experiment done by Geiger in addition to Marsden. Modern View of the Atom For an atom, which always has no net electrical charge, the number of negatively charged electrons around the nucleus equals the number of positively charged protons in the nucleus.

Scientists have been able to obtain computer-enhanced images of the outer surface of atoms using the scanning tunneling microscope (STM) in addition to the atomic as long as ce microscope (AFM). Structure of the Atom Isotopes Isotopes of the same element have the same number of protons in addition to electrons but differ in the number of neutrons. Atomic Mass The atomic mass as long as each element on the periodic table reflects the relative abundance of each isotope in nature. Definitions Atomic number is the number of protons in the nuclei of the atoms of an element Mass number or atomic mass is the number of neutrons plus number of protons in the nucleus of an atom Mass number = ’s of protons + ’s of neutrons Ex. How many protons, neutrons, in addition to electrons are in atom of gold (Au) with a mass number of 197 Protons = 79; Electrons = 79; Neutrons = 197 – 79 = 118; Isotopes are atoms of the same element having different mass numbers.

Definitions cont Atomic mass unit (amu) is the unit as long as relative atomic masses of the elements; 1 amu =1/12 the mass of carbon-12 isotope. 1 amu = 1.6605×10-24 grams Atomic weight is the number that represents the average atomic mass of the element’s isotopes weighted by percentage abundance. Isotopes H 1 1 H 1 2 H 1 3 Write the nuclear symbols as long as atoms with the following subatomic particles. A. 8 p+, 8 n, 8 e- — B. 17p+, 20n, 17e- — C. 47p+, 60 n, 47 e- — Learning Check

A. 8 p+, 8 n, 8 e- 16O 8 B. 17p+, 20 n, 17e- 37Cl 17 C. 47p+, 60 n, 47 e- 107Ag 47 Solution Learning Check 1. Which of the following pairs are isotopes of the same element 2. In which of the following pairs do both atoms have 8 neutrons A. 15X 15X 8 7 B. 12X 14X 6 6 C. 15X 16X 7 8 Solution B. 12X 14X 6 6 Both nuclear symbols represent isotopes of carbon with six protons each, but one has 6 neutrons in addition to the other has 8. C. 15X 16X 7 8 An atom of nitrogen (7) in addition to an atom of oxygen (8) each have 8 neutrons.

Isotopes of Magnesium In naturally occurring magnesium, there are three isotopes. 24Mg 25Mg 26Mg 12 12 12 Isotopes of Mg Relative Masses of Atoms Use atomic weights of the elements to calculate molecular weights (MW) of compounds Relative masses provide a simple way of comparing the masses of atoms. Ex. The mass of neon atoms is 20.18 in addition to the mass of calcium atoms is 40.08. Ca atom mass Ne atom mass = 40.08 20.18 = 1.986 Mass of Calcium is 2x than Ne He atom mass H atom mass = 4.003 1.008 = 3.971 Mass of Helium is 4x than Hydrogen The exact relationship between two masses calculated

Calculating the atomic weight of compounds MW = CnHmOk MW = n(at. Wt. C) + m(at. Wt. H) + k(at. Wt. O) H2O the MW is MW = 2(at. Wt. H) + 1(at. Wt. O) MW = 2(1.008 u) + 1(15.996 u) MW = 18.012 u or 18.01 u as long as water Use atomic weighs from the periodic table inside the front cover of your book to determine the molecular weight of urea, CH4N2O, the compound by which much nitrogenous body waste is excreted in the urine. Learning Check a. 58.02 u b. 62.25 u c. 60.06 u Solution MW = n(at. Wt. C) + m(at. Wt. H) + k(at. Wt. O) The chemical as long as mula as long as urea is CH4N2O, MW = 1(12.01 u) + 4(1.008) + 2(14.01) + 1(16.00) MW = 60.062 u or rounded off 60.06 u

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Models of the Atom The Plum Pudding Model Electrons are embedded in a sphere of positive charge. The Nuclear Model All of the positive charge is in a tiny central nucleus with electrons outside the nucleus. This model was developed by Ruther as long as d after his l in addition to mark experiments. The Ruther as long as d Experiment Models of the Atom (continued) Bohr Model or the Solar System Model Niels Bohr in 1913 introduced his model of the hydrogen atom. Electrons circle the nucleus in orbits, which are also called energy levels. An electron can “jump” from a lower energy level to a higher one upon absorbing energy, creating an excited state. The concept of energy levels accounts as long as the emission of distinct wavelengths of electromagnetic radiation during flame tests. Niels Bohr (1885-1962)

Bohr’s Orbit Model Definitions Quantum is the smallest increment of energy, as long as example, in an atom emitting or absorbing radiation. Ground state is the condition of an atom in which all electrons are in their normal, lowest energy levels. Excited state is an unstable, higher energy state of an atom. A line spectrum as long as hydrogen Fig. 3-6a, p. 49 Neon (Ne)

Solution Select the element in each pair with the larger atomic radius. A. K B. K C. P Key Words Chemistry Matter Pure substance Mixture Element Compound Homogeneous mixture Heterogeneous mixture States of matter Solid Liquid Gas Physical changes Chemical changes Atom Molecule Periodic table Periods Groups or Families Main group elements Key Words (cont) Transition elements Metals Nonmetals Semimetals Protons Neutrons Electrons Atomic number Mass number Isotopes Atomic Mass Nucleus Electromagnetic radiation Wavelength Energy level Ground state Excited state Orbital Electronic configuration Valence electrons Outer shell

Wills, Brad Meteorologist

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