Chapter 2 (2.4, 2.5, 2.6)
Section 2.6 Review
- the periodic table was originally developed using atomic masses and the chemical and physical properties of the elements, but it is now known that the atomic numbers, not atomic masses, are the basis for the properties of an element. - the modern periodic table is arranged in order of increasing atomic number - the organization of elements in the periodic table makes it easier to identify the similarities and differences among different elements - elements in the same group in the periodic table generally have similar chemical properties
Ne has 10 protons and 10 electrons. The common charges of the elements close to Ne all would like to have...
10 electrons
Ex: 2.15 In the modern periodic table, locate two pairs of naturally occurring elements besides iodine and tellurium that are out of order, based on their atomic masses.
??
Ex: 2.16 which element begins the fourth period of the periodic table? Which element ends it? How many elements are in that period?
??
Ex: 2.17 select the period and group where each of the following elements is located: neon, Ne, rubidium, Rb; tungsten, W; and francium, Fr. Which of these elements have similar chemical properties?
??
Ex: 2.12 Weighted Grades - in a particular class, exams are worth 50% of the overall grade, quizzes, are worth 25% of the overall grade, homework is worth 20% of the overall grade, & class participation is worth 5% of the overall grade. - A particular student has earned an average score of 80.2% on the exams, 77.3% on the quizzes, 87.8% on the homework assignments, and 100% on the class participation. What is the student's overall grade in the course?
Exams 0.50 80.2 0.5 x 80.2% = 40.1% Quizes 0.25. 77.3 0.25 x 77.3% = 19.325% Homework. 0.20. 87.8 0.20 x 87.8% = 17.56% Participation 0.05. 100.0 0.05 x 100% = 5%
electrons are found outside the nucleus and makeup...
essentially all of the volume of the atom; electrons are negatively charged
Ex: 2.7 how many protons, neutrons and electrons are in a neutral atom of each of the following isotopes? c) 20^N 10
# p+ = 10 this defines it as neon # e- = 10 because it's neutral # n^0 = 10
Ex: 2.7 how many protons, neutrons and electrons are in a neutral atom of each of the following isotopes? a) 32^S 16
# p+ = 16 this defines it as sulfur # e- = 16 because it is neutral # n^0 = 16
Ex: 2.7 how many protons, neutrons and electrons are in a neutral atom of each of the following isotopes? b) 19^F 9
# p+ = 9 this defines it as Fluorine # e- = 9 because it is neutral # n^0 = 19-9 = 10
Ex: 2.7 how many protons, neutrons and electrons are in a neutral atom of each of the following isotopes? d) 238^U 92
# p+ = 92 this defines it as uranium # e- = 92 because it is neutral # n^0 = 10
Nonmetals, Metals, and Metalloids
- metals make up the majority of elements and are located on the left side of the periodic table - metals have specific properties; they are shiny, malleable and ductile, and conductors of heat and electricity - nonmetals consist of hydrogen plus the elements on the upper-right side of the table and are brittle as solids - metalloids are the elements that border these two larger categories and share properties with both metals and nonmetals
Group
- alkali metals - alkaline earth metals - coinage metals - halogens - noble gases
Electrons Count in ions
- atoms can lose and gain e-s to become charged particles called IONS - we should know common ion charges. Just remember that each element wants to have the same #e's as it's closest neutral NOBLE GAS
Section 2.5 atomic masses (overview)
- calculate the atomic mass of any element from the masses and abundances of its naturally occurring mixture of isotopes
Section 2.6 ---> The Periodic Table (overview)
- discuss the contributions of Mendeleev and Meyer that led to the development of the periodic table - classify the elements in a systematic manner based on their location in the periodic table - identify periods, groups and sections of the periodic table by name and number.
Calculation of atomic mass
- elements often exist as a mixture of multiple isotopes that have different isotope masses - the atomic mass of an element is the weighted average of the masses of the naturally occurring isotopes
Development of the Periodic Table
- elements with similar chemical characteristics have been grouped together in various ways over time - the PERIODIC TABLE is the result of many years of refining this grouping
Isotopes of Hydrogen
- have same atomic number (which defines it as hydrogen) - have different mass number (different number of neutrons)
Section 2.5 Review
- historically, atomic mass was determined from mass ratios, such as those used to develop the law of definite proportions. Today, the mass and percent occurrence of each isotope are used. - atomic mass is the weighted average of the masses of the naturally occurring mixture of isotopes of an element. Do not confuse the atomic mass with the mass number, A, which is the total number of protons and neutrons in the atom.
Section 2.4 - subatomic particles, isotopes, and ions (objectives)
- identify the mass number of any atom using the number of each type of subatomic particle - protons, electrons, and neutrons - present in that atom, or vis versa - identify which element an atom represent using the mass number of that atom, or vis versa
Relative sizes and masses
- if an electron had the mass of a marble, a proton or neutron would have the mass of a bowling ball - if the entire nucleus were the size of a marble, the atom would be the size of a stadium
Electron count in neutral atoms
- if you have a neutral atom, then the number of electrons HAS to be equal to the number of protons.
Elements
A molecule composed of one kind of atom; cannot be broken into simpler units by chemical reactions. - the number of protons defines an element (each element has a unique number of protons in its nucleus)
Neutral F has 9 e-s. A common ion would form by...
ADDING 1e- to form F-1
Atomic mass you will have to do calculation with fractional abundances. If you are given percents ---> make sure to change to fraction. We need to know how to do these calculations - calculate the atomic weight of boron, B, from the following data Isotope Isotopic Mass (g/mol) Fractional Abundance B-10. 10.013 0.1978 B-11. 11.009 0.8022
ANWSER B-10: 10.013 x 0.1978. = 1.9805 B-11: 11.009 x 0.8022 = 8.8314 == 10.812 g/mol
Isotopes of elements
Atoms of the SAME element with a different number of neutrons. Do not influence the chemical properties of an element. - isotopes have the same atomic number, but they have different masses because of the different numbers of neutrons - each isotope of an element is usually identified by it's MASS NUMBER
Ex: 2.13 Calculate the atomic mass of copper, given that naturally occurring copper consists of 69.17% 63^Cu, which has an isotope mass of 62.9396 g/mol, and 30.83%. 65^Cu, which has an isotope mass of 64.9278 g/mol.
Fractional abundance Molar Mass g/mol multiple 0.6917 62.9396 43.5353 0.3083. 64.9278 20.0172 SUM = 63.55
Neutral Na has 11e-s. It can mimic Ne e-# by...
LOSING 1e- to form Na+1
The eight "A" groups are called...
MAIN GRUOPS (or representative) elements
Properties of Subatomic Particles
Mass of each more specifically (u)+ proton: 1.0073 neutron: 1.0087 electron: 0.000549
Atomic mass
The average mass of all the isotopes of an element - each isotope has its own characteristic mass - the % of each isotope remains relatively constant
Ex: 2.18 classify the following elements as main group elements, transition elements, or inner transition elements. a) Cs b) In c) U
a) Cs ----> Main group b) In ------> Main group c) U --------> Inner transition elements
Ex: 2.11 How many protons & electrons are in each of the following ions? a) F- b) Mg^2+ c) N^3- d) W^6+
a) F- ?? b) Mg^2+ ?? c) N^3- ?? d) W^6+ ??
Ex: 2.19 which of the following elements are metals and which are nonmetals? a) calcium, Ca b) phosphorus, P c) nickel, Ni d) the carbon in a diamond, C
a) calcium, Ca ----> metals b) phosphorus, P ----> nonmetal c) nickel, Ni ------> metal d) the carbon in a diamond, C ------> nonmetal
ex: 2.8 a) 6^C 14 b) O-17 c) H2 d) 14^N 6 e) S-6
a) incorrect atomic # = # protons --> 14^C 6 b) O-17 correct 17^O 8 c) H2 incorrect atomic # = # protons, ----> H1 d) 14^N incorrect atomic # = # protons 7N 6 e) S-6. incorrect # protons for S = 16, thus the mass number (A) has to be larger than 6 16S
Ex: 2.20 a) the 5th element in the first row of transition metals b) the element of the 4th period that is also in group 6 c) the 7th transition element d) the first element of group 8 e) the 3rd halogen f) the first alkaline earth metal g) the first coinage metal
a) vanadium b) Tellurium c) Cobalt d) Helium e) Argon f) Beryllium g) Copper
Ions are formed when...
an atom gain or loses electrons
Initially, elements were ordered by...
atomic mass
Atomic #, Z
atoms are electrically neutral because the number of protons, p, equals the number of electrons, e. # of p+ = # of e- *the atomic # Z is the number of protons in an atom's nucleus z = p
Positively charged ions are called ___________________, whereas negatively charged ions are called __________________.
cations, anions
The charges given are relative charges, based on the...
charge on the electron, e, as the fundamental unit of charge (1 e = -1.60 x 10^-19 C) - + the masses are given in atomic mass units, u
A group....
consists of the elements in any one COLUMN of the periodic tables. Columns of elements have similar properties (the group columns are numbered)
A period...
consists of the elements in one HORIZONTAL ROW of the periodic table <----------->
The fractional abundance
fraction of the total number of atoms of an element that is composed of a particular isotope 16^O 17^O 18^O 8 8 8 99.759%. 0.037%. 0.204%
On the periodic table, elements are arranged ___________________ in order of increasing atomic number and grouped ___________________ by similar properties
horizontally vertically
Atoms with different numbers of neutrons but the same number of protons are...
isotopes of each other.
Magnesium atoms can LOSE 2 electrons, forming a positively charged...
magnesium CATION Mg ---> Mg^2+ + 2e-
Subatomic particles
neutrons, protons, electrons are called SUBATOMIC PARTICLES - the atomic nucleus is incredibly tiny, with a radius only 1/10,000 the radius of the cell - the nucleus contains almost all the mass of the atom - electrons have very little mass, but occupy almost all the volume of the atom
protons and neutrons are both found in the...
nucleus and account for essentially all the mass of the atom; protons are positively charged, whereas neutrons are electrically neutral. The mass number A is the total number of protons and neutrons in the atom.
The atomic number, Z, is equal to the...
number of protons in the nucleus and determines which element the atom is identified as
Oxygen atoms can gain electrons, forming a negatively charged...
oxide ANION O + 2e- ----> O^2-
After Dalton's hypothesis was published, many scientists worked to determine...
relative atomic masses of the known elements - two scientists, Dimitri Mendeleev and Lothar Meyer, combined the known atomic masses and the known elemental characteristics to produce a periodic table. - However, Mendeleev used his periodic table to predict the existence and properties of yet - to - be discovered elements - Mendeleev chose to place the elements I and Te in opposite order than their atomic masses would suggest, placing them with elements of similar properties. His assumption that their masses were incorrectly determined, proved to be correct.
Atoms are composed of...
subatomic particles (protons, neutrons, electrons)
The Mass Number
the TOTAL number of protons PLUS neutrons in the nucleus of an atom A = #p+ + #n^0 THIS IS NOT AN ATOMIC WEIGHT. IT DOES NOT APPEAR ANYWHERE ON THE PERIODIC TABLE
weighted averages
the atomic masses given on the periodic table are the WEIGHTED AVERAGES of the actual masses of the naturally occurring isotopes of that element. - the weighted averages take into account the relative numbers of each type of isotope - of course, we can have pure isotopes, and then the mass is only that of the single isotope.
Noble Gases
the noble gases are colorless, odorless, and mostly inert - these were not discovered until after the periodic table was first developed
Atomic Number Z
the number of protons in the nucleus of an atom - the elements are arranged on the Periodic Table in order of their atomic numbers
