Q2: Gen Bio Flashcards
father of atomism, focused on the ultimate components of all substances.
Believed that Matter is ultimately composed of indivisible particles, with nothing between them but empty space.
DEMOCRITUS (c.460-370 BC)
atoms Greek atomos, “”
uncuttable
held that it was impossible for “nothing” to exist, and his influence suppressed the concept of atoms for 2000 years.
ARISTOTLE (384-322 BC)
Further studies in the 18TH CENTURY gave rise to ______
laws concerning the relative masses of substances that react with each other.
- 2 mass laws discovered (law of mass conservation, law of definite proportions)
At the beginning of the 19TH CENTURY,______________
John Dalton proposed an atomic model that explained these mass laws.
Early 20TH CENTURY gave rise to ________________
a picture of the atom with a complex internal structure, which led to our current model.
matter having an invariant chemical composition and distinct properties
PURE SUBSTANCE
fundamental substance, cannot be separated into simpler substances by chemical methods
- Simplest type of matter with unique physical and chemical properties
- Consist of only one kind of atom
- Substance, matter whose composition is fixed
Element
Why are each element unique?
because the properties of its atoms are unique
Most elements exist in nature as ____
population of atoms
an independent structure consisting of 2 or more atoms chemically bound together.
molecules
substance composed of 2 or more elements in Fixed proportion; can be separated into simpler substances and elements only by chemical methods
- type of matter composed of two or more different elements that are chemically bound together.
Compound
consists of fixed numbers of atoms of the component elements.
Compound
T or F. properties of compounds are different from those of its component elements
T
What process do compounds undergo during its breakdown
Chemical change/Chemical process
matter consisting of 2 or more pure substances that retain their individual identities and can be separated by physical methods since they are physically intermingled
MIXTURE
T or F. components of a mixture don’t vary in their parts by mass.
F - components of a mixture can vary in their parts by mass.
T or F. A mixture retains many of the properties of its components.
T
Unlike compounds, mixtures can be separated into their components by________
by physical changes;
mixture having a uniform composition and properties throughout
- also called??
Homogeneous ; Solution
no visible boundaries because the components are mixed as individual atoms, ions, and molecules.
Homogeneous Mixture
T or F. We have no way to tell visually whether an object is a substance (element or compound) or a homogeneous mixture.
T
T or F. Solutions can only exist in the liquid state
F - can exist in all 3 physical states
mixture not uniform in composition and properties throughout.
Heterogeneous
has one or more visible boundaries between the components
Heterogeneous mixture
most elements consist of a large collection of ___________ atoms
identical
Mixtures differ fundamentally from compounds in three ways:
- the proportions of the components can vary
- the individual properties of the components are observable;
- the components can be separated by physical means
Separation of mixture though hands
HANDPICKING
separates the grains from the stems or stalks. this is beating wheat or paddy stems to separate grains from the stems and the chaff that covers the grains
THRESHING
process of separating husk from grains using the wind.
Winnowing
This method involves the separation of magnetic substances from non-magnetic substances by means of a magnet.
Magnetization or Magnetic Attraction
done to separate mixtures that contain substances mostly of different sizes. The mixture is passed through the pores of the sieve. All the smaller substances pass through easily while the bigger components of the mixture are retained.
Sieving
process by which heavier impurities present in liquid normally water settle down at the bottom of the container containing the mixture. The process takes some amount of time.
Sedimentation
Separating of mixture though pouring
Decantation
Separation of mixture through centrifugal force
Centrifugation
separate a mixture of solids containing one which sublimes and one (or more than one) which does not, by heating the mixture.
Sublimation
separates the components of a mixture on the basis of differences in particle size. It is used most often to separate a liquid (smaller particles) from a solid (larger particles).
Filtration
separates mixtures based on differences in solubility, a measure of how much solid substance remains dissolved in a given amount of a specified liquid.
the least soluble of the dissolved substances, the one that is least likely to remain in solution, usually forms crystals first, and these crystals can be removed from the remaining solution by filtration.
Crystallization
based on differences in solubility. In a typical procedure, a natural (often plant or animal) material is ground in a blender with a solvent that extracts (dissolves) compound(s) embedded in an insoluble material. This extract is separated further by the addition of a second solvent that does not dissolve in the first. After shaking in a separatory funnel, some components are extracted into the new solvent
Extraction
process that depends on the different abilities of substances to form gases.
Distillation
Used to separate miscible liquids with different but very close boiling point.
Fractional Distillation
The differing abilities of substances to adhere to the surfaces of solids can also be used to separate mixtures.
Chromatography
(literally, “the writing of colors”),
chromatography
What conclusion can be derived when the ray bends in magnetic field in the cathode ray tube experiment?
It consists of charged particles
What conclusion can be derived when the ray bends toward positive plate in electric field in the cathode ray tube experiment
IT consists of negative particles
What conclusion can be derived when the ray is identical for any cathode in the cathode ray tube experiment
Particles are found in all matter
A cathode ray forms when ______
high voltage is applied to a partially evacuated tube
The rays were called cathode rays because ______________
they originated at the negative electrode (cathode) and moved to the positive electrode (anode).
T or F. the ray is identical no matter what metal is used as the cathode.
T
Cathode ray particles were later named __________
electrons.
the British physicist __________________used magnetic and electric fields to measure the ratio of the cathode ray particle’s mass to its charge.
J. J. Thomson (1856–1940)
In 1909, the American physicist _____________________ measured the charge of the electron.
Robert Millikan (1868–1953)
Si unit for charge
C (coulomb)
__________ proposed a model of a spherical atom composed of diffuse, positively charged matter, in which electrons were embedded like “raisins in a plum pudding.”
Thomson
In 1896 the French scientist ____________ discovered that a compound of uranium spontaneously emits high-energy radiation. This spontaneous emission of radiation is called _____________
Henri Becquerel (1852–1908) ; radioactivity.
In 1910, the New Zealand–born physicist _____________ used one type of radioactive particle in a series of experiments that solved this dilemma of atomic structure.
Ernest Rutherford (1871–1937)
Rutherford calculated that an atom is mostly space occupied by electrons, but in the center of that space is a tiny region, which he called the _________, that contains all the positive charge and nearly all the mass of the atom.
nucleus
He proposed that positive particles lay within the nucleus and called them protons.
Rutherford
- Rutherford’s model it could not account for all the atom’s mass.
- After more than 20 years, this issue was resolved when, in 1932, ___________discovered the neutron
James Chadwick
an uncharged dense particle that also resides in the nucleus
neutron
An atom is an electrically ______, spherical entity composed of a positively charged central _______ surrounded by one or more negatively charged _______.
neutral; nucleus; electrons
T or F. The electrons move slowly within the available atomic volume, held there by the attraction of the nucleus.
F. - The electrons move rapidly within the available atomic volume, held there by the attraction of the nucleus.
The nucleus is incredibly dense: it contributes ______% of the atom’s mass but occupies only about ________ of its volume. An atom’s diameter about ________times the diameter of its nucleus.
99.97; 1 ten-trillionth; 10,000
An atomic nucleus consists of protons and neutrons (the only exception is _______)
the simplest hydrogen nucleus, which is a single proton).
An atom is neutral because
the number of protons in the nucleus equals the number of electrons surrounding the nucleus.
What are the absolute charges of proton, electron, & neutron?
Proton = +1.60218x10^(-19) C
Neutron = 0
Electron = -1.60218x10^(-19) C
What are the relative masses of proton, electron, & neutron?
Proton = 1.00727 amu
Neutron = 1.00866 amu
Electron = 0.00054858 amu
Relative charges of P, N, and E
1+
0
1-
Absolute masses of P, N, & E
P = 1.67262 x 10^(-24)
N = 1.67493 x 10^(-24)
E = 9.10939 x 10^(-28)
__________ of an element equals the number of protons in the nucleus of each of its atoms.
atomic number (Z)
All ______ of a particular element have the same atomic number
atoms
The total number of protons and neutrons in the nucleus of an atom is its ___________
mass number (A).
The atomic number (Z) is written as a left _______ and the mass number (A) as a left ________ to the symbol.
subscript; superscript
number of neutrons (N) equals the ___________
mass number minus the atomic number
All atoms of an element are identical in atomic number but not in __________
mass number
___________of an element are atoms that have different numbers of neutrons and therefore different mass numbers.
Isotopes
A key point is that the chemical properties of an element are primarily determined by the number of _________, so all isotopes of an element have nearly identical chemical behavior, even though they have different masses.
electrons
mass of an atom is measured relative to the __________________
mass of an atomic standard
The modern atomic mass standard is the __________. Its mass is defined as exactly ___ atomic mass units.
carbon-12 atom; 12
atomic mass is also called as
atomic weight
average of the masses of an element’s naturally occurring isotopes weighted according to their abundances
atomic mass
In 1871, the Russian chemist _____________ organized information into a table that listed the elements by increasing atomic mass, arranged so that elements with similar chemical properties fell in the same column.
Dmitri Mendeleev
The modern periodic table of the elements, based on Mendeleev’s earlier version—but arranged by __________, not mass—is one of the great classifying schemes in science and has become an indispensable tool for chemists.
atomic number
Each element has a box that contains its _______, _______, and ______
atomic number, atomic symbol, and atomic mass
how many groups and periods are there in the periodic table
7 periods
18 groups
The 8 A groups contain the ______ group
main group or representative elements
the 10 B groups between 2A and 3A contain the ________
transition elements
2 horizontal series of _________ fit between the elements in Group 3B and Group 4B and are usually placed below the main body of the table
Inner transition elements, the lanthanides and actinides
in general, elements in a group have _______chemical properties and elements in a period have ________ chemical properties.
similar ;different
It is the _________ of the atoms of interacting elements that are involved in compound formation
electrons
Elements combine in two general ways:
- Transferring electrons - ionic comp
- Sharing electrons - Covalent comp
Ionic compounds are composed of ______, charged particles that form when an atom (or small group of atoms) gains or loses one or more electrons.
ions
simplest type of ionic compound is a_____________________, one composed of just two elements. It typically forms when a metal reacts with a nonmetal.
binary ionic compound
______ atoms transfer electrons to the _______atoms.
metal; nonmetal
T or F. All binary ionic compounds are solids
T
A cation or anion derived from a single atom is called a ___________.
monatomic ion
Ionic compounds are _________; that is, they possess no net charge. For this to occur, they must contain equal numbers of positive and negative charges—not necessarily equal numbers of positive and negative ions.
neutral
metals ____ electrons and nonmetals _____ electrons to form ions with the same number of electrons as in an atom of the nearest noble gas [Group 8A(18)].
lose; gain
- Noble gases have a stability (low reactivity) that is related to their ____________
number (and arrangement) of electrons.
form when elements share electrons, which usually occurs between nonmetals.
covalent compounds
Nonmetals that exist as diatomic molecules at room temp:
as tetratomic molecules:
as octatomic molecules:
Nonmetals that exist as diatomic molecules at room temp:
- N2, O2, F2, Cl2, Br2, I2, H2
as tetratomic molecules:
- P4
as octatomic molecules:
- S8 and Se8
Most covalent substances consist of ____________
molecules.
Covalent Bonds Within Ions
Polyatomic Ions
consist of two or more atoms bonded covalently and have a net positive or negative charge
Polyatomic ions
3 types of chemical formulas
- Empirical
- Molecular
- Structural
Shows the relative # of atoms of each element in the compound; simplest type; derived from the masses of component elements
Empirical Formula
shows the actual # of atoms of each element in a molecule of a compound
Molecular compound
shows the # of atoms and the bonds between them; placement and connections of atoms
Structural formula
Ionic compounds are ________________ rather than separate molecular units
arrays of oppositely charged ions
We write a formula for the _______ unit which gives the relative #s of cations and anions in the Ionic compound
formula unit
T or F. The ionic compound has zero net charge thus positive charges must balance neg charges
T
What type of formula is generally used in ionic compounds
empirical formulas
