chem chapter 1
Terms
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- Matter
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-Anything that has mass and takes up space
-all matter is made up of various combinations of the simple forms of matter called the chemical elements. An element is a substance that consists only of one kind of atom - substance
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-each different pure kind of matter
-a single, pure for of matter, not a mixture of several different kinds of matter (not flesh softdrinks b/c they are complex mixtures) - pure
- the same throughout, even on a microscopic scale
- analysis
- identification of the substances mixturex contain
- chemical elements
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-basic building blocks of matter and in various combinations make up all the matter on Earth
-define elements on the basis of differences at teh atomic level - atom
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-smalles particle of an element
-comes from teh Greek word "not cuttable"
-1st argument made by JOHN DALTON - John Dalton
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-first thought of the idea of atom in 1807
-oxygen adn magnesium experiement: found that the mass of oxygen is proportional to that of magnesium - element
- substance composed of only one kind of atom
- macroscopic
- -the level that deals with the properties of large, visible objects
- microscopic level
- -level that can not be seen with the eye
- sympolic language
- ties macro and microscopic levels together by describing macroscopic changes in terms of atoms
- chemical symbol
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-the one or two letters tah represent individual elements
-found int he periodic table - What is the most abundant element in universe?
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(in terms of the # of atoms)
HYDROGEN - What are the most abundant elements in the crust of the earth?
- Oxygen and silicon
- What are the most abundant elements in teh human body?
- hydorgen, oxygen and carbon
- Model of atoms
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1. Atoms are mad eup of subatomic particles called electrons, protons, and neutrons
2. The protons and neutrons form a compact, ecntral body called the nucleus of the atom
3. The electrons are distributed in a space like cloud around the nucleus - subatomic particle
- A particle smaller than an atom (ex: proton, neutron, electron)
- electron
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e-
-A negatively charged subatomic particle found outside the nucleus of an atom
-much less massive than a proton, nearly 2000 times lighter - neutron
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n
-An electrically bneutral subatomic particle found in the nucleus of an atom
-it has the approximately the same mass as a proton, thereby not affecting teh charge (neutral) but add substantially to the mass of the atom
-known jointly with protons as NUCLEONS - proton
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p
A positively charged subatomic particle found in the nucleus of an atom - nucleus
- central body of an atom formed by a protons and neutrons
- nuclear atom
- model of an atom
- JJ Thomson
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-1897 earliest experimental evidence for the existence of an internal structure of atoms
-investigated "cathode rays"
found that the charged particles were the same regardless of teh metal he sed for the cathode and measured the ratio of thier charges to their mass
- therefore discovered electrons - cathode rays
- rays that are emitted from a metal electrode (electrical contact) when a high potential difference (hight voltage) is applied between that electrode and another one in an evacuated glass tube
- mass of electron
- 9.109 * 10 ^-28 g
- What is the charge of atoms?
- Overall zero atoms hvae zero charges, whcih is ehy each atomj must contain enough positive charge to cancel the negative charge
- alpha particles
- ∠streams of positively charged particles. These particles came from a sample of teh radioactive gas radon
- Atomic nucleus
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-pointlike positively charged region
-dense pointlike centers of positive charge surrounded by a large calume of mostly empty space - Where are electrons in atom?
- Thinly distrubuted throughout the space around the nucleus.
- atomic number
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-the number of protons in an atomic nucleus
-first accurately determined by HG Moseley
-Ex: hydrogen has one proton so we know the atomic number is 1
-= to the number of electrons outside the nucleus -
Nuclear Atom
(general) -
-All + charge adn alsomst all teh mass in concentrated in a tiny nucleus
- the - charged electrons surround the nucleus like a cloud
-atomic number is teh number of protons in teh nucleus
-there is an equal number of electrons outside the nucleus - Mass spectrometer
- -A device that can be used for determining the mass of a given type of atom
- nucleons
- neutrons adn protons that are found in the nuclus (because they are very similar particles)
- mass number
- total number of protons and neutrons in a nucleus
- Isotopes
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-Atoms with the same atomic number (belonging to the same element) but different mass numbers
-have teh same number of protons but different numbers of neutrons
-named by writing its mass number after the name of the element (i.e. neon -20, neon-21)
-Its symbol is written by adding the mas number as a superscript to the left of the chemical symbol
Sometimes the atomic number is included as a subscript on teh lower left
-name comes from Greek work for "equal place" - Big Bang
- According to current ideas, hydrogen and helium were formed in teh big Bang. The heavier elements were made inside stars adn then scattered throughout space
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