Chemistry Chapter 4

Define atom using your own words

- smallest component of an element + exhibits all of the characteristic properties of that element

State what quantities are conserved when balancing a nuclear reaction

-- the number of particles and the total charge - a constant number of particles does NOT imply that mass is conserved

Classify each as a chemical reaction, a nuclear reaction, or neither. 1. Thorium emits a beta particle. 2. Two atoms share electrons to form a bond. 3. A sample of pure sulfur emits heat energy as it slowly cools. 4. A piece of iron rusts

1= nuclear reaction 2= chemical reaction 3= neither 4= chemical reaction

How much heavier is an alpha particle than an electron

2 protons=2 unit 2 neutrons= 2 unit 1 alpha particle= 4 mass units 1e-=1/1840 mass units 1 alpha particle x 4 mass units/1 alpha particle x 1e-/ 1/1840= 7360e-

Explain how Dalton's theory of the atom and the conservation of mass are related

Dalton explained atoms are not created or destroyed in chemical reactions, only rearranged

Contrast the methods used by greek philosophers and Dalton to study the atom

Democritus and Aristotle could not conduct experiments to verify their hypothesis, whereas Dalton could make careful measurements.

Six atoms of Element A combine with 8 atoms of element B to produce is compound particles. How many atoms of elements A and B does each particle contain? Are all atoms used to form compounds?

Each compound contains 1 atom A and 1 B 2 atoms of element B are not used - No, some are used to form covalent bonds

Thomson's Plum Pudding Model (look at notes)

Electrons are spread throughout the atom

Explain how the existence of isotopes is related to the fact that atomic masses are not whole numbers

They represented weighted averaged of the masses of isotopes of an element

How does each type of radiation affect the atomic number and the mass number of an atom

alpha decay: p=-2, n=-2= -4 mass (new element now) Helium ion w/ plus 2 charge beta decay: mass stays same, but number of proton changes gamma decay: doesn't alter protons or neutrons. effect of moving nucleus from unstable to stable position. Usually happens after alpha or beta

Explain how unstable atoms gain stability

atoms with unfilled outer shells will usually form chemical bonds with other atoms to achieve stability/ emit alpha particle, beta or gamma ray

Explain how the type of atom is defined

by the atomic number

Describe the structure of a typical atom. Identify where each particle is located.

central + small dense nucleus that contains p and n - nucleus surrounded by cloud of negatively charged electrons

Evaluate the experiment that led to the conclusion that electrons are negatively charged particles found in all matter

deflection towards positively charged plates demonstrated negatively charged nature of electrons - since changing type of electrode/type of gas used in cathode ray did not affect the ray produced led to conclusion=electrons present in all matter

Compare the relative charge + mass of each of the subatomic particles

e: 1-, relative mass: 1__1840 n= 0, relative mass: 1 p=1+, relative mass: 1

Aristotle matter ideas

empty space cannot exist - matter is made up of fire, air, earth + water

Rutherford's nuclear atomic model

explains the results of the gold foil experiment. Most alpha particles pass straight through, being only slightly deflected by electrons if at all. strong force of repulsion btwn positive nucleus and the positive alpha particles causes large deflections.

Democritus matter ideas

matter composed of atoms= move through empty spaces - atoms solid, homogeneous + indestructible (dalton also) - dif/ kinds of atoms have different shapes + sizes - size, shape + movement of atom determine properties of matter

Summarize Dalton's Atomic Theory

matter composed of small particles= atoms and are indivisible - atoms of same element identical in size, mass + chemical properties - atoms-specific element= r different from atoms of a dif/ element - dif/ atoms combine in simple-whole number ratios to form compounds - chemical reaction= atoms separated, combined or rearranged

Which subatomic particle identifies an atom as that of a particular element

proton

Compare + contrast Thomson's plum pudding model with Rutherford's nuclear atomic model

they both believed that atoms contained negatively charged electrons - unlike plum pudding model--where atoms simply floated in "soup", Rutherford believed they orbited the central nucleus