atomsAll matter is composed of very tiny particles, which Dalton called atoms. moleculeA molecule is...
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Transcript of atomsAll matter is composed of very tiny particles, which Dalton called atoms. moleculeA molecule is...
What are atoms made of? ▪ Know the three subatomic particles and
their relative charges and masses – Table 2.1
▪ Know that a neutron is modeled as an electron + a proton
▪ Define amu, why it exists and the conversion between amu and grams
▪ Distinguish between mass number and atomic number
▪ Know how to write the mass and atomic numbers in a formula
• All matter is composed of very tiny particles, which Dalton called atomsatoms.
• A moleculemolecule is a tightly bound combination of two or more atoms that acts as a single unit.
10-15 m
Neutron
Proton
Nucleus (protons and neutrons)
Space occupied by electrons
10-10 m
Subatomicparticle
Mass(g)Charge
Location in an atom
Proton
Electron
Neutron
1.6726 x 10-24
9.1094 x 10-28
1.6749 x 10-24
1
0.0005
1
+1-1
0
In the nucleus
Outside the ucleus
In the nucleus
1.0073
1.00875.4859 x 10-4
Mass (amu)
Mass (amu);to one
significantfigure
1 amu = 1.6605 x 10-24 g
2.2 - Classifying Matter ▪ Define the terms element,
compound, mixture, pure substance, homogeneous and heterogeneous mixtures
▪ Learn the system for classifying matter
Element:Element: a substance (for example, carbon, hydrogen, and iron) that consists of identical atoms.
There are 116 known elements.Of these, 88 occur in nature; the others have been made by chemists and physicists.
• Monatomic elements:Monatomic elements: consist of single atoms; for example, helium (He) and neon (Ne).
• Diatomic elements:Diatomic elements: there are seven elements that occur as diatomic molecules:– H2, N2, O2, F2, Cl2, Br2, and I2
• Polyatomic elements:Polyatomic elements: some elements have three or more atoms per molecule:– O3, P4, S8
– diamond has millions of carbon atoms bonded together to form one gigantic cluster.
• Compound:Compound: a pure substance made up of two or more elements in a fixed ratio by mass.
• Formula of a compound:Formula of a compound: tells us the ratios of its constituent elements and identifies each element by its atomic symbol.– NaCl: the ratio of sodium atoms to chlorine atoms
in sodium chloride is 1:1
– H2O: the ratio of hydrogen atoms to oxygen atoms in water is 2:1
• Mixture:Mixture: a combination of two or more pure substances– The substances may be present in any mass ratio.– Each substance has a different set of physical
properties.– Mixtures may be homogeneous or heterogeneous.– If we know the physical properties of the individual
components of the mixture, we can use appropriate physical means to separate the mixture into its component parts.
Homo- or Heterogeneous mixture?Pure substance or compound?
2.3 – Atomic Theory ▪ Understand the Law of Conservation of Mass ▪ Know that an atom CANNOT be divided by an ordinary
chemical reaction.
• Law of Conservation of Mass– Matter can be neither created or destroyed.– As Dalton explained, if matter is made up of
indestructible atoms, then any chemical reaction just changes the attachments among atoms, but does not destroy the atoms themselves.
OPb PbO C OOC
Carbonmonoxide
Leadoxide
Carbon dioxide
Lead
+ +
OWL 2.3
2.4 – What are atoms made of? ▪ Define the word isotope and how it
relates to the number of neutrons of a particular type of atom
▪ Know the two conventions for writing isotopes
▪ Define atomic weight ▪ Define the atomic weight of the
average atom (what’s in the periodic table)
• Isotopes:Isotopes: atoms with the same number of protons but a different number of neutrons.– carbon-12 has 6 protons and 6 neutrons;– carbon-13 has 6 protons and 7 neutrons;– carbon-14 has 6 protons and 8 neutrons;
• Most elements found on Earth are mixtures of isotopes:– chlorine is 75.77% chlorine-35 (18 neutrons) and
24.23% chlorine-37 (20 neutrons).
C136C
136
C126C
126
C146C
146
• Mass number:Mass number: the number of protons and neutrons in the nucleus of an atom.– the mass of the electrons in an atom is so small
compared to that of its protons and neutrons that electrons are not counted in determining mass number.
• Atomic number:Atomic number: the number of protons in the nucleus of an atom.
• a carbon atom of this composition is referred to as carbon-12.
Mass number (number of protons & neutrons)Atomic number (number of protons)6
12C
• Atomic weight:Atomic weight: the weighted average of the masses (in amu) of the naturally occurring isotopes of an element.– example: chlorine is 75.77% chlorine-35 and
24.23% chlorine-37
75.77100
x 34.97 amu + 24.23100
x 36.97 amu = 35.45 amu
chlorine-35 chlorine-37 17Cl
35.4527
atomic weight in the Periodic Tableis given to four
four decimal places
2.5 - The Periodic Table ▪ Apply the words Group and Period ▪ Know the location of the metals, nonmetals, main group
elements, halogens, alkali metals, alkali earth metals, transition metals, inner transition metals, halogens, and noble gases
2.6 & 2.7 – The arrangement of “ground state” electrons in atoms ▪ Know the components of an electron configuration
o Principal energy level (“shell”) o Orbital - Orbital shapes and orientaions
▪ Relate electron configurations to the Periodic Table ▪ Know how to write an electron configurations ▪ Know how to write orbital “box” diagrams and how they
relate to orientations of orbitals
8A
1s7A6A5A4A3A
2B1B8B8B
1A
8B7B
2A
6B5B4B3B
1
2
3
4
5
6
7
1
2
3
4
5
6
7
6
7
Main group elements;s block (2 elements)
Transition elements;d block (10 elements)
Main group elements;p block (6 elements)
1s
Helium is also an s blockelement
3d
4d
5d
3p
4p
6d
2s
3s
4s
5s
6s
7s
2p
5p
6p
7p
4f
5f
Inner transition elements; f block
(14 elements)