Lab 1: accuracy and density Objective: • To understand the meaning of accuracy and precision—You will determine the relative precision and accuracy of different glassware items.
Water displacement • To learn to measure volumes and masses (using volumetric glassware and top-loading balances).
Water displacement • To determine the density of solid samples using water displacement method
Prelab • Summary of the procedure in your own words in notebook • Typed or in your notebook answer the prelab questions. • Submit before lab start • Post lab report due a week after the lab. • Prelab 5pts and lab report 20pts
Lab report • Lab report guide: • 1. Results • Tables neatly filled out with data • Proper significant figures • Legible sample calculations • 2. Error Analysis • Determination of percent error (for glassware and metal densities) • Typed discussion of measured results vs literature results and description of possible sources of error. Note that “human error” is not an acceptable answer. Please be specific. • 3. Post Lab Questions • Typed answers to the Post Lab questions
Classification of matter Chemistry is the study of matter Matter is every thing around you, it is anything that has mass and occupies space (volume). Most pure Most impure
Elements • Anelement is a pure substance that cannot be broken down into simpler substances by a chemical reaction. • Each element is identified by a one- or two-letter symbol • Example: • The element carbon is symbolized by C • The element chlorine is symbolized by Cl • When two letters used the first is capital and the second is small case letter • Example • Co is a symbol for cobalt • And CO is carbon monoxide.
Elements’ symbols • most symbols are derived from the first 1 or two letter of the element name • 11 elements have symbols derived from the latine or German orgins.
Elements and the periodic table • Elements are arranged in the periodic table based on their chemical properties.
Question 2.33 • Give the name of the elements in each group of three elements symbols. • Use the periodic table to find the element corresponding to each symbol. • a. Au, At, Ag • gold, astatine, silver • b. N, Na, Ni • nitrogen, sodium, nickel • c. S, Si, Sn • sulfur, silicon, tin • d. Ca, Cr, Cl • Calcium, chromium, chlorine
Elements and the periodic table The elements in the periodic table are divided into three groups—metals, nonmetals, and metalloids. Metals: • They are located on the left side of the periodic table. • They are good conductors of heat and electricity. • Metals are shiny solids at room temperature, except for mercury (Hg), which is a liquid.
Elements and the periodic table Nonmetals: • They are located on the right side of the periodic table. • Nonmetals have a dull appearance • They are usually poor conductors of heat and electricity. • Nonmetals can be solids, liquids, or gases at room temperature solid liquid gas bromine nitrogen oxygen sulfur carbon
Elements and the periodic table Metalloids: • These are located on the solid line that starts at boron (B) and angles down towards astatine (At). • Metalloids have properties intermediate between metals and nonmetals • Only seven elements are Metalloids: antimony (Sb) tellurium (Te) astatine (At) boron (B) silicon (Si) germanium (Ge) arsenic (As)
Problem 2.4 • Locate each element in the periodic table and classify it as a metal, nonmetal, or metalloid. • a. titanium d. palladium g. selenium • b. chlorine e. arsenic h. osmium • c. krypton f. cesium • Metals are shiny materials that are good conductors of heat and electricity. Nonmetals do not have a shiny appearance, and they are generally poor conductors of heat and electricity. Metalloids have properties intermediate between metals and nonmetals. • a, d, f, h: metals b, c, g: nonmetals e: metalloid
Elements and the human body The building block elements: oxygen, carbon, hydrogen and nitrogen . Major Minerals: K, Na, Cl, Mg, S, Ca and P. Trace Elements: As, B, Cr, Co, Cu, F, I, Fe, Mn, Mo, Ni, Se, Si and Zn.
Elements and the human body Major Minerals (macronutrients): Example: K, Na and Cl present in body fluid, Mg and S in protiens, Ca and P in teeth and bones. Trace Elements (micronutrients): Example: Fe is needed for hemoglobin the protein that caries oxygen Zn is needed proper function of enzymes in the liver and kidney I is needed for thyroid function
Compounds Compound: a pure substance formed by chemically combining two or more elements together. A chemical formula consists of: • Element symbols to show the identity of the • elements forming a compound. • Subscripts to show the ratio of atoms in the • compound. H2O H2O C3H8 C3H8 2 H atoms 1 O atom 3 C atoms 8 H atoms
Compounds • Compounds can be drawn many ways: • Different elements are represented by different • colors:
Structure of the Atom All matter is composed of the same basic building blocks called atoms. Atoms are composed of three subatomic particles:
Structure of the Atom Nucleus ElectronCloud Nucleus: Electron cloud: • location of protons • andneutrons • dense core of the atom • location of most of the • atom’s mass • location of electrons • comprises most of the atom’s volume
Structure of the Atom • Opposite charges attract while like chargesrepel each other. • Protons and electrons attract each other, buttwo electrons repel each other.
Structure of the Atom From the periodic table: Atomic number (Z) is the number of protons in the nucleus. 3 Li • Every atom of a given element has the same • number of protons in the nucleus. • Different elements have different atomic numbers. • A neutral atom has no net overall charge, so Z = number of protons = number of electrons
Atomic Weight The atomic weight is the weighted average of the masses of the naturally occurring isotopes of a particular element reported in atomic mass units. From the periodic table: atomic number 6 C 12.01 element symbol atomic weight (amu)
Isotopes, Atomic Number, and Mass Number Isotopes are atoms of the same element that have a different number of neutrons. the number of protons (Z) Mass number (A) = + the number of neutrons Mass number (A) 35 Cl Atomic number (Z) 17 # of protons = 17 # of electrons = 17 # of neutrons = 35 – 17 = 18
Isotopes in medicine • Generally the chemical properties of isotopes are identical. • Some isotopes of elements are radioactive • Radioactive isotopes have diagnostic and therapeutic uses • Iodine 131 is used take an image of the thyroid
Atomic Weight HOW TO Determine the Atomic Weight of an Element What is the atomic weight of chlorine? Example List each isotope, it’s mass in atomic mass units, and it’s abundance in nature. Step  Mass (amu) Isotope Isotopic Abundance Cl-35 34.97 75.78% = 0.7578 Cl-37 36.97 24.22% = 0.2422
Atomic Weight HOW TO Determine the Atomic Weight of an Element Multiply the isotopic abundance by the mass of each isotope, and add up the products. Step  The sum is the atomic weight of the element. 34.97 x 0.7578 26.5003 amu = 36.97 x 0.2422 = 8.9541 amu 35.45 amu 35.4544 amu = 4 sig. figs. Answer 4 sig. figs.
Problem 2.12 • How many protons, neutrons and electrons are contained in each atom with the given atomic number and mass number? • a. Z= 17, A=35 • number of protons = atomic number (Z)= 17 • Mass number (A) = number of (protons + neutrons)= 35 • Neutrons = 35 – 17 = 18 • Electrons = protons = 17 • b. Z = 14, A = 28 • number of protons = atomic number (Z)= 14 • Mass number (A) = number of (protons + neutrons)= 28 • Neutrons = 28 – 14 = 14 • Electrons = protons = 14
Basic Features of the Periodic Table A row in the periodic table is called a period, and a column in the periodic table is called a group.
Basic Features of the Periodic Table Main group elements: • They consist of the tall columns on the right and left of the Periodic Table. • The groups are numbered 1A–8A. Transition metal elements: • These are in the 10 short columns in the middle. • The groups are numbered 1B–8B. Inner transition elements: • They consist of the lanthanides and actinides. • There are no group numbers assigned. 35
Characteristics of Groups 1A and 2A Elements that comprise a particular group have similar chemical properties. Properties of Both Groups • soft and shiny metals • low melting points • good conductors of heat and electricity • react with water to form basic solutions Group Number Group Name 1A Alkali metals Alkaline earth elements 2A
Characteristics of Groups 7A and 8A Group Number Group Name Properties • exist as two atoms joined together • very reactive 7A Halogens • very stable • rarely combine with any other elements Noble gases 8A
The Unusual Nature of Carbon • Carbon’s ability to join with itself and other elementsgives it a versatility not seen with any other element in the periodic table. • Elemental forms of carbon include the following carbon-only structures:
The Unusual Nature of Carbon The way the carbons are bonded together gives the physical properties of diamond vs graphite
Problem 2.19 • Identify each highlighted element in the periodic table and give it’s • titanium, Ti, group 4B (or 4), period 4, transition metal • phosphorus, P, group 5A (or 15), period 3, main group element • dysprosium, Dy, no group number, period 6, inner transition element
Problem 2.17 Give the period and group number for each element: a. oxygen; b. calcium; c. phosphorous; d. platinum; e. iodine.