(substance that cannot be broken down into further substances) Atom (smallest unit of an element) – subatomic particles (neutrons‚ protons‚ electrons) Compound (2 or more) Atomic number - # of protons Atomic mass = # of neutrons and protons Ion – total number of electrons doesn’t equal # of protons (anion gained electrons‚ cation lost electrons) Electron shells‚ orbitals‚ valency‚ rule of 8 Bonds = ionic‚ covalent (polar‚ nonpolar)‚ hydrogen‚ Van der walls Electronegativity Relationship of
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ionic lattice 4.1.2 Group 1 metals form +1 ions‚ group 2 metals form +2 ions‚ metals in group 3 form +3 ions . Examples : Li+‚ Mg2+‚ Al3+. Greater ease of ionisation Li->Cs is due to the increased electron shielding of the nuclear attraction caused by additional inner shells of electrons. The easier atoms are to ionise‚ the more reactive they will be because less energy is required to ionise them‚ and so they react faster. 4.1.3 Group 5 will form 3- ions‚ Group 6 ions will form 2- ions
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water takes to reach its destination. This can be applied in the variables of resistance. The electrons ’bounce ’ off the atoms - this causes the electrons to head elsewhere rather than the desired direction. In a long tube there are more atoms‚ this slows the electrons down as they ’bounce ’ off into another direction. In a short tube‚ there are less atoms which means there are less to deflect the electron any more speeding the speed up. In theory‚ the length should be proportional to the resistance
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The History of the Atom Hypothesis according to Aristotle (350 BC): All matter consists of the elements earth‚ air‚ fire‚ and water. Experiment: A tree grows from the earth as water is added. The tree is then set on fire in an effort to form new elements. 1. What kind of results would be observed from this experiment? Fire‚ ash (earth)‚ smoke (air) 2. Would these observations support or reject the hypothesis? Explain. Support. No elements have been produced that are something other than
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Photoelectric effect Shining light on a metal causes electrons to be emitted Below some frequency‚ no photons are emitted regardless of intensity of light. As frequency of the light increases‚ the kinetic energy of the emitted electrons increase. As the intensity of the light increases under a certain frequency‚ the number of the electrons ( current I) increases. Photon energy is quantized. Some energy is needed to liberate an electron form a material. This amount of energy is called the
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1. How is electricity produced? The most simple way of producing static ekectricity is by rubbing or friction. When you rub two different kind of materials that are insulator‚ you can transfer electrons from one substance to another. Nowadays‚ to create electricity we use battery and generators. Voltage can be made by heart‚ light or mechanical pressure. http://science.howstuffworks.com/electricity-info2.htm 2. Where and how is electricity used? Electricity gives us ability to produce
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XRD – X-Ray Diffraction X-ray diffraction (XRD) is a powerful non-destructive technique for characterizing crystalline materials. It provides information on structures‚ phases‚ preferred crystal orientations (texture)‚ and other structural parameters‚ such as average grain size‚ crystallinity‚ strain‚ and crystal defects. X-ray diffraction peaks are produced by constructive interference of a monochromatic beam of X-rays scattered at specific angles from each set of lattice planes in a sample. The
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are __________ paired and __________ unpaired electrons in the Lewis symbol for a phosphorus atom. A) 4‚ 2 B) 2‚ 4 C) 2‚ 3 D) 4‚ 3 E) 0‚ 3 2-There are __________ paired and __________ unpaired electrons in the Lewis symbol for a phosphorus atom. A) 4‚ 2 B) 2‚ 4 C) 2‚ 3 D) 4‚ 3 E) 0‚ 3 3- How many unpaired electrons are there in an ion? A) 0 B) 1 C) 2 D) 3 E) This cannot be predicted. 4-What is the electron configuration for the ion? A) B) C)
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Since the birth of Physical Review Letters fifty years ago‚ condensed matter physics has seen considerable growth‚ and both the journal and the field have flourished during this period. In this essay‚ I begin with some general comments about condensed matter physics and then give some personal views on the conceptual development of the field and list some highlights. The focus is mostly on theoretical developments. DOI: 10.1103/PhysRevLett.101.250001 PACS numbers: 01.30.−y The transistor
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able to appear because an excited electron was unstable and had to fall back to a more stable energy level‚ creating energy in the form of light. However‚ to understand this‚ one must understand what causes an electron to be excited. So from the very beginning‚ a person named Max Plank proposed a theory that energy is emitted and absorbed in quantities called “quanta.” Einstein then came along and said that light contained quanta energy called “photons.” Electrons that are present in atoms are on
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