atoms, ions and molecules Flashcards
chapter 2
what is the chemists’ view of an atom?
all matter is made up of atoms, and atoms are made up of the subatomic particles: electrons, protons, and neutrons
what is a proton?
determines the identity (element) of the atom
what is an electron?
determines the relative electric charge of the atom
what was the first subatomic particle discovered?
the electron
What experiment did J.J. Thomson perform and what did he conclude from it?
-he used an apparatus known as a cathode ray tube and found that the phosphorous gas in the tube excites electrons when a current passes through. A green light would appear where electrons were. The light would move when exposed to a magnet.
-discovered that the particles that make up the cathode ray are charged and are a part of all matter. Identified the existence of electrons
what experiment did Robert Millikan perform and what did he conclude?
-used an apparatus in which an X-ray beam ionized N2 and O2 by making them lose electrons. As the oil drops passed through the beam, they picked up electrons. Between the positive and negative plate, the drops start to fall because of gravity then stop because of an attraction to the positive plate
-discovered that there is an exact charge for electrons
what was the model of the atom created by J.J. Thomson?
-the plum pudding model
-proposed that the electrons were distributed evenly through a homogenous sphere of positive charge
What was Ernest Rutherford’s experiment and what did he conclude?
-radioactive alpha particles were created from aluminum and shot at a gold foil. Majority of the particles traveled through the foil, but some particles were scattered
-concluded that there is a small, centralized nucleus in an atom that is positively charged
what would’ve happened in Rutherford’s model if the plum pudding model was true? Why did he come to the conclusion he did based on the experiment?
-if the plum pudding model was correct, the alpha particles would push through the gold foil
-the alpha particles that scattered did so because of the condensed nucleus containing protons
what is the location, symbol, relative charge, and relative mass of an electron?
-outside the nucleus
-e-
- -1
- 1/1836
what is the location, symbol, relative charge, and relative mass of a proton?
-inside the nucleus
- p+
- +1
- 1
what is the location, symbol, relative charge, and relative mass of a neutron?
-inside the nucleus
- n0
-0
- 1
what is an isotope?
atoms of the same element with varying number of neutrons in the nucleus
what is an atomic number?
each element has a characteristic number of protons in the nucleus
what is the atomic mass number?
total number of protons and neutrons in he nucleus
what is nuclide notation?
used to display the number of protons and neutrons in the nucleus
in nuclide notation, where are the mass number, atomic number, and number of electrons located?
-mass number- top left of the element
-atomic number- bottom left of the element
-number of electrons- top right of the element
what is the periodic table?
a tabular arrangement of elements in rows and columns, highlighting the regular repetition of properties of the elements
what is a period on the periodic table?
the elements in one horizontal row
what is a group (family) on the periodic table?
the elements in one vertical column. These elements have the most similarities between elements and how they react
where are the nonmetals located on the periodic table?
-H in period 1 group 1
-elements above the staircase from group 14-18
where are the metalloids located on the periodic table?
-on the staircase in groups 13-16
where are the transition metals located on the periodic table?
-from group 3-12
where are the main group metals found on the periodic table?
-group 1 and 2
-below the staircase in groups 13-16
what are metals? Name all characteristics.
-solids with high melting points and high densities and have bright, metallic luster
-good conductors of heat and electricity
-malleable- can be hammered into thin sheets
-ductile- can be drawn into fine wires
-majority of elements
-form cations with positive charges (loses electrons)
what are nonmetals? Name all characteristics.
-typically have low melting points and low densities and have a dull appearance
-poor conductors of heat and electricity
-not malleable or ductile and crush into a powder when hammered
-eleven nonmetals occur naturally in the gaseous state
-form anions with negative charges (gains electrons)
what are the characteristics of metalloids?
have properties midway between those of metals and nonmetals
where are the noble gases located on the periodic table?
group 18
where are the halogens located on the periodic table?
group 17
where are alkaline earth metals located on the periodic table?
group 2
where are alkali metals located on the periodic table?
group 1 minus H+
which nonmetals occur naturally as diatoms (7)?
-Hydrogen (H2)
-Nitrogen (N2)
-Oxygen (O2)
-Fluorine (F2)
-Chlorine (Cl2)
-Bromine (Br2)
-Iodine (I2)
what is an atomic mass unit (amu)?
a unit used to express the relative masses of atoms and subatomic particles
what is the equation for a weighted average?
(mass)(abundance) + (mass)(abundance) = average mass
what is the atomic mass of copper if 63-Cu has atomic mass of 62.930 amu and 69.09% abundance and 65-Cu has a mass of 64.928 amu and an abundance of 30.91%?
63.55 amu
- (62.930)(0.6909) + (64.928)(0.3091)
what is a mole?
a unit for a specific number; convenient unit for expressing microscopic quantities involved in macroscopic processes we observe. It is the smallest unit we can see of atoms or molecules
what is Avogadro’s number (1 mole)
6.022 x 10^23
what is the molar mass?
the mass (in grams) equal to the mass of an individual atom or molecule (amu)
what is a molecular mass?
mass of one molecule of a molecular compound; it can be found with the sum of the atomic masses of the atoms in that compound
what is a formula mass?
mass in atomic mass units of one formula unit of an ionic compound
if given the mass of an element, what steps would you take to find the moles of the element?
divide by the molar mass
if given the mass of an element, what steps would you take to find the atoms of the element?
- divide by the molar mass
- multiply by Avogadro’s number
if given the compound H2O, what steps would you take to find the mass of the element H
- divide by Avogadro’s number
- use the chemical formula
- multiply by the molar mass
In Rutherford’s gold-foil experiment, only a small fraction of alpha particles were reflected back towards the alpha source. As a result, what can we conclude about the atom?
only a small region of the atom has a positive charge
Thomson obtained the value of -1.759 x 10^11 C/kg (Coulombs/kilogram) for the charge-to-mass (e/m) ratio for the electron. Millikan determined the charge (e) on the electron to be -1.602 x 10^-19 C. What is the mass of the electron?
9.107 x 10^-31 kg
- (1 kg/-1.759 X 10^11 C) x -1.602 x 10^-19 C
Two stable isotopes of an element have isotopic masses of 10.0129 amu and 11.0093 amu. The atomic mass is 10.81. Which isotope is more abundant?
The isotope with a mass of 11.0093 is more abundant
Calculate the mass, in grams, of 10 copper atoms
1.055 x 10^-21 g
-(10 atoms/ 6.022 x 10^23)= 1.661 x 10^-23
-1.661 x 10^-23 x 63.55 (molar mass) =
what is the group number of titanium?
4
what is the period number of sodium?
3
how many atoms are in 4.35 x 10^3 moles?
2.62 x 10^27
this type of element is malleable, ductile, has high melting and boiling points, and form cations
metals
this type of element is not malleable or ductile, has low melting and boiling points and form anions
non-metals
what family does fluorine belong to?
halogens
which of the following is not a diatomic element: Hydrogen, bromine, chlorine, or carbon
carbon
who determined the charge of an electron and what did he use?
-JJ Thompson
-cathode ray tube
who determined the charge of an electron?
Robert Millikan
Who proposed a subatomic model (plum pudding model) of the atom?
JJ Thomson
who found out that there is a nucleus in the atom separating + and - charge?
Rutherford
a metal sample is hammered into a rectangular sheet with an area of 31.2 ft^2 and an average thickness of 2.30 x 10^-6 cm. If the mass of this sample is 0.4767 g, predict the identity of the metal. (1 in = 2.54 cm)
a. aluminum (2.70 g/cm^3)
b. copper (8.95 g/cm^3)
c. gold (19.3 g/cm^3)
d. zinc (7.15 g/cm^3)
d. zinc (7.15 g/cm^3)
which statement is not true concerning cathode rays?
1. they originate from the negative electrode in a cathode ray tube
2. they travel in straight lines in the absence of electric or magnetic fields
3. they are made up of electrons
4. the properties of cathode rays are dependent on the cathode material
- the properties of cathode rays are dependent on the cathode material
the ion X2+ has 24 electrons. What is a possible identity for X?
Fe
which of the following is a correct statement:
a. tin is a transition element
b. lead is a nonmetal
c. antimony is a metalloid
d. elements are arranged in order of increasing atomic mass
c. antimony is a metalloid
what is the relationship between frequency and wavelength?
frequency is inversely proportional to wavelength
