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Physics Test Notes

Notes for Chapter 17 Test

atoms the building blocks of matter
why are atoms important? they make up everything in the universe we see, feel, taste, hear, and smell
explain what atoms are the smallest particles of an element that can be identified with that element
what is an element? a substance made of only one kind of element
how many elements are known today and how many of those are naturally occurring? more than 115 known today, 90 are naturally occurring
how are unnatural elements made? they are man made in laboratories using atomic accelerators and nuclear reactors
what comes from a pantry of less than 100 elements? every single, complex, living, or nonliving substance in the known universe
how much material on earth is formed from only a dozen elements? 99%
are most elements common? no most elements are relatively rare
what elements make up living things? oxygen, carbon, hydrogen, nitrogen, and calcium
what is a chemical symbol? the letter or letters that represent an element. the first letter is always capitalized and the additional letters are lowercased
why are the 16 most common elements important? they are critical for life
describe hydrogen it is the lightest element, makes up over 90% of all the atoms in the universe
describe helium second lightest element, makes up most of the remaining 10% of atoms in the universe, although this element is rare on earth
how are heavier elements formed? by fusion reactions inside stars, elements heavier than iron formed during supernovas
how are the heaviest elements formed? when pairs of neutron stars, the super dense cores of supernovas, collide
what are most of the atoms on earth? the remains of stars
what does dark matter compose? 23% of the matter in the universe
what do astrophysicists believe about this dark matter? that it is made up of particles not yet detected
how many atoms are in a thimbleful of water? 10 to the 23, there are more atoms in a thimbleful of water than there are drops of water in all the lakes and rivers of the world
how do atoms move? they are constantly moving, slow in solids, faster in liquids, fastest in gases
how long does it take for one of your breaths to become evenly mixed in the atmosphere? 6 years
why are atoms too small to be seen with visible light? because light is made of waves and atoms are smaller than the wavelength of light
how old are different atoms? they are older than the material they compose, some are as old as the universe itself, others are at least as old as the sun and earth
how long have atoms in your body been around? since long before the solar system came into existence, more than 4.6 billion years
how do atoms recycle? migrate around, withing, and throughout, breathing in and out, scratching your skin, coughing and sneezing
do we own our atoms? no, they will later be used by other living and non living things
we are all made of the same atoms
when did the idea of atoms begin? in 400 BC by the Greeks
what did John Dalton do in the 1800s? said matter was made of atoms by studying chemical reactions
who was Robert Brown? a scottish botanist who in 1827 studied pollen grains under a microscope, he noticed the spores were in constant motion he first thought they were alive
what is brownian motion? evidence that atoms exist as it results from the motion of neighboring atoms and molecules, they bump into the larger particles we can see, it is the constant jiggling of particles just large enough to be seen
what are newer microscopes? an electron beam
what is a molecule? the smallest particle of a substance consisting of two or more atoms that bond together by sharing electrons
what can molecules be made of? the same element or different elements
what is the most common molecule? water, H2O, water is a polar molecule, 2 hydrogens, 1 oxygen
what other matter is usually made of molecules? gas or liquid, nitrogen N2, oxygen, O2
what are complex molecules? DNA,composed of millions of atoms
is all matter made of molecules? no, metals are rows of individual atoms, crystalline minerals, table salt
are individual atoms small? yes, too small to be seen with optical microscopes, but they can be seen with electron microscopes
how can molecules be detected? by all of our senses, even smell
which molecules move quickly? molecules of gas
what is a compound? a substance that is made of atoms of DIFFERENT elements combined in a fixed proportion
what does the chemical formula of a compound tell? the proportions of each kind of atom, shows the symbols of the elements present, shows the number of atoms of each element (subscript position)
is a compound always made of molecules? they may or may not be, water and carbon dioxide are made of molecules, table salt is made of different kinds of atoms arranged in a regular pattern, every chlorine atom is surrounded by 6 sodium atoms, every sodium atom is surrounded by 6 chlorine atoms
what are the properties of compounds? compounds have properties different from those of the elements of which they are made, H2O, hydrogen and oxygen are both gases, water is a liquid
what are atoms like? they are mostly empty space, the mass of an atom is primarily concentrated in the nucleus
what is the nucleus of an atom? the central region of the atom, first discovered by ernest rutherford in 1911 in his famous gold foil experiment, it contains most of the mass of the atom, occupies less than a trillionth of the volume of the atom, it has a positive charge
what prevents close packing of the atomic nucleus? electrical repulsion, only under special circumstances are the nuclei of two or more atoms squashed into contact, nuclear fusion takes place, it occurs in the stars and in a hydrogen bomb
what are nucleons? the building blocks of the nucleus
what are neutrons? electrically neutral, all neutrons are identical
what are protons? electrically charged positive, all protons are identical
what is atomic mass number? the total number of nucleons in the nucleus of an atom, protons plus neutrons
do all atoms have the same number of protons? atoms of various elements differ in the number of protons
what is atomic number? the number of protons in the nucleus
what are isotopes? atoms of the same element having different numbers of neutrons
what is electrical charge? it comes in 2 kinds, positive = protons, negative = electrons
what effects do different charges have on each other? like charges repel, unlike charges attract, protons repel protons but attract electrons, electrons repel electrons but attract protons
how are protons held together in the nucleus? by a strong nuclear force (stronger than electric force at very small distances)
what are electrons? they orbit the nucleus, are negatively charged subatomic particle, have very little mass, have 1/1800 of the mass of a proton or neutron, they do not significantly contribute to the mass of the atom
what type of charge do atoms have? they are electrically neutral, the number of negatively charged electrons must equal the number of positively charged protons, when the number of electrons is more or less than the number of protons in the atom, the atom is no longer neutral
atoms electrical charge, cont and has a net charge and is now called an ion
what is the shell model of the atom? a model in which the electrons of an atom are pictured as grouped in concentric shells around the nucleus
how many shells can an atom have? up to 7 different shells and each gas its own capacity for electrons, the first shell can hold 2, the second shell can hold up to 8, the outer shell cannot hold more than 8
what does the arrangement of electrons do? dictates the atom's physical and chemical properties, melting and freezing points, electric conductivity, taste, texture, appearance, and color, ability to combine with other elements
what do atoms do to have 8 electrons in the outer shell? atoms will share or transfer electrons, then they form a chemical bond
what is bonding? attraction between protons and electrons can cause atoms to combine
what is a covalent bond? forms when 2 atoms share electrons
what is an ionic bond? when electrons are transferred between atoms
when are ions of opposite charge formed? when electrons are transferred and these ions are held together by simple electric forces
what is the periodic table? a chart that lists atoms by their atomic number and by their electron arrangement
what are some patterns of the periodic table? from left to right, each element has one more proton and electron than the preceding one, down, each element has one more shell filled to its capacity than the element above
what is a group? describes elements that are in the same column of the periodic table, they have similar chemical properties because their outermost electrons are arranged in a similar fashion
Created by: distler



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