the end of the number are ALWAYS significant. 4) ALL zeroes which are to the left of a written decimal point and are in a number >= 10 are ALWAYS significant. 5) If you can/must get rid of the zeroes‚ then they are NOT significant NOTES: -The electron was discovered by using experiments with CATHODE rays in the late 1800s -Ernest Rutherford discovered the nucleus in 1911 -Atoms of different elements combine in whole number ratios to make compounds. -In chemical reactions‚ atoms are combined
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element (TRUE) 10. Models of the atom a. Plum Pudding- electrons float around in a positive charged “pudding” b. Nuclear Model- atom is mostly empty space. All the positive charge and almost all the mass is concentrated in a small area in the center‚ called the nucleus. Nucleus is composed of protons and neutrons c. Planetary- electrons orbit the nucleus like planets d. Quantum-atom is found inside a blurry electron cloud 11. Scientists – Thomson‚ Rutherford‚ Millikan‚ etc.
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between electrons and nuclei‚ or as the result of a dipole attraction. The strength of chemical bonds varies considerably; there are "strong bonds" such as covalent or ionic bonds and "weak bonds" such as dipole–dipole interactions‚ the London dispersion force and hydrogen bonding. Since opposite charges attract via a simple electromagnetic force‚ the negatively charged electrons that are orbiting the nucleus and the positively charged protons in the nucleus attract each other. Also‚ an electron positioned
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taking the electrons from the bond with it. The more stable the leaving group as an independent assemblage‚ the more readily it will depart the molecule. Carbocation: A carbon with only 6 shared valence shell electrons. A full positive charge resides on the carbon. Carbocations are electrophiles. Nucleophile: An atom or assemblage of atoms which will donate electrons to form a new covalent bond. Strong nucleophiles are strong Lewis bases. Electrophile: An atom which will accept electrons and form
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charged protons and neutrally charged neutrons an electron cloud of negatively charged electrons An atom is a neutral particle containing an equal number of protons and electrons Molecule: a group of two or more atoms held together by chemical bonds Ion: an atom that has a positive or negative charge cation: lost electrons; takes on a positive charge (more protons than electrons) anion: gained electrons; takes on a negative charge (more electrons than protons) Chemical Bonds: form between atoms
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that scientists use as a premise for almost every study. The kind of atoms is the first one that the material is made up of. You will have your neutral elements and your compound elements. The neutral elements have the same amount of protons and electrons‚ which basically cancel each other out leaving them neutral. The compound element deals with combining more than one element. In the way those atoms are arrange is the second one. The best example of this is by comparing the atoms of liquid and the
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types of radiation with matter 1.Atomic Spectroscopy 2.Molecular spectroscopy • Important to understand the interaction between the electromagnetic radiation and the matter (mainly)‚ + interaction of a acoustic waves and beam of particles (ions‚ electrons) with matter. • Wave model failed to account for absorption and emission of EM energy – (sinosoidal wave model (λ ‚ f‚ v‚ Amplitude) • Particle model : EM radiation is viewed as stream of discrete particles or wave packets‚ of energy called
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photosynthesis and precipitation: Respiration- oxygen is taken in and carbon dioxide and water are given out Oxidation- a loss of electrons and a increase in oxygen Photosythesis- converting light energy into glucose Precipitation- to create a solid into a solution Protons neutrons and electrons : Protons are positive with a mass of 0.99 Neutrons have no charge and have a mass of 1 Electrons have a negative charge and a mass of 0.0005 What is PH: A scale that measurers how acidic or alkaline a substance if
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Element name-Helium Element Symbol-He Atomic number-2 Group name or number- Part of the noble gases in group 18 Atomic mass (to nearest thousandth)-4.003 Number of protons-2 Number of neutrons-2 Number of electrons-2 Number of valence electrons-2 List of isotopes-He3 and He4 Electron Configuration-1s2 Discovered By-Pierre Janssen Year discovered-1868 Circumstances of discovery- Janssen discovered helium in 1868 when he was looking in a telescope when he found the yellow spectrum lines of helium
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water molecule (2) In a water molecule two hydrogen atoms form single polar covalent bonds with an oxygen atom. “Oxygen is more electronegative (6 valence electrons) - region around oxygen has partial negative charge. Hydrogen is less electronegative (1 valence electron) -region near the two hydrogen atoms has a partial positive charge.” (3) A water molecule is a polar molecule with opposite ends of the molecule with opposite charges. Fig.2. Positively
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