Science: Atoms and Isotopes Flashcards

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Questions and Answers

What did Democritus theorize in 450 BCE?

the existence of atoms in the void

What accurate measurements did Antoine Lavoisier theorize in the 1780s?

the composition of chemical compounds and that compounds containing more than one element always had the same relative amounts of each element

What was John Dalton's discovery about matter?

Matter is divisible but not infinitely divisible; the smallest unit he named atom.

What does H₂O represent in chemistry?

water Signup and view all the answers

What does CO₂ represent in chemistry?

carbon dioxide Signup and view all the answers

What does CH₄ represent?

methane Signup and view all the answers

What formula represents acetic acid?

CH₃COOH Signup and view all the answers

CH₃CH₂CH₃ is a chemical formula for ______.

propane Signup and view all the answers

What does the atomic mass of Nitrogen ⁷N refer to?

14.007 Signup and view all the answers

What is the significance of the atomic number?

It represents the total number of protons in an atom. Signup and view all the answers

How can you calculate the number of neutrons using the atomic number and the mass number?

Neutrons = mass number - atomic number Signup and view all the answers

What is conventional representation in terms of an atom?

Mass number, symbol of element, atomic number Signup and view all the answers

What did Rutherford's gold foil model lead to the discovery of?

the nucleus Signup and view all the answers

What did Thomson's Plum Pudding Model suggest?

That the atom is like a plum pudding, with a ball of positive charge and negative electrons inside. Signup and view all the answers

What is the formula for calculating the mass number?

Protons + neutrons Signup and view all the answers

What is an isotope?

An atom that has the same number of protons but a different number of neutrons. Signup and view all the answers

What happens when you decrease or increase the number of neutrons in an atom?

It may become unstable and gain or lose weight. Signup and view all the answers

What is used to identify an element?

Protons Signup and view all the answers

What is the pattern in each group of the periodic table?

They will all have the same number of valence electrons. Signup and view all the answers

How do atoms form ions?

By giving or losing electrons. Signup and view all the answers

Why will atoms form ions?

When they are exposed to radiation, or to form chemical bonds. Signup and view all the answers

Study Notes

Historical Theories and Discoveries

Democritus theorized in 450 BCE the existence of atoms in a void.
Antoine Lavoisier in the 1780s emphasized accurate measurements in chemical compounds, establishing that compounds with multiple elements consistently maintain the same relative amounts of each.
John Dalton discovered that matter is not infinitely divisible, proposing the term "atom" for the smallest indivisible part of matter.

Chemical Compounds

Water (H₂O) consists of 2 hydrogen atoms and 1 oxygen atom, in a 2:1 ratio.
Carbon dioxide (CO₂) comprises 1 carbon atom and 2 oxygen atoms, in a 1:2 ratio.
Methane (CH₄) has 1 carbon atom and 4 hydrogen atoms, in a 1:4 ratio.
Acetic acid (CH₃COOH) comprises 2 carbon, 4 hydrogen, and 2 oxygen atoms, in a 1:2:1 ratio.
Propane (CH₃CH₂CH₃) contains 3 carbon and 8 hydrogen atoms.
Butane (CH₃CH₂CH₂CH₃) has 4 carbon and 10 hydrogen atoms, with a ratio of 2:5.

Atomic Structure

Nitrogen (⁷N): 7 protons, atomic mass 14.007, and 7 neutrons.
Oxygen (⁸O): 8 protons, atomic mass 15.999, and 8 neutrons.
Calcium (²⁰Ca): 20 protons, atomic mass 40.078, and 20 neutrons.
Sodium (¹¹Na): 11 protons, atomic mass 22.990, and 12 neutrons.
Sulfur (¹⁶S): 16 protons, atomic mass 32.066, and 18 neutrons.
Chlorine (¹⁷Cl): 17 protons, atomic mass 35.453, and 18 neutrons.

Subatomic Particles

Protons: Located in the nucleus, positively charged, with a mass of approximately 1.
Neutrons: Also in the nucleus, have no charge, and a mass of about 1.
Electrons: Found in electron shells, negatively charged, with negligible mass.

Atomic Numbers and Mass

The atomic number indicates the total number of protons in an atom.
The mass number represents the total of both protons and neutrons.
Neutrons can be calculated from mass number minus atomic number, with atomic mass being the weighted average of isotopes.
Relative mass number accounts for the average of the isotopes of an element.

Isotopes and Stability

Isotopes are atoms with the same number of protons but differing numbers of neutrons, potentially leading to instability when neutron numbers vary.

Periodic Table Patterns

Each group in the periodic table shares the same number of valence electrons, influencing chemical behavior.
Atoms can form ions by gaining or losing electrons, commonly occurring during radiation exposure or chemical bonding.

Chemical Reactions and Formulas

The reaction forming aluminum sulfide is represented as Al³⁺ + S²⁻ resulting in Al₂S₃.
Sodium chloride forms through Na¹⁺ + Cl¹⁻ creating NaCl.

Calculating Atomic Mass

Relative atomic mass is computed based on the contribution of different isotopes’ masses and their quantities relative to total isotope counts.

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Description

Explore key concepts in atomic theory and radiation with these interactive flashcards. Delve into the contributions of scientists like Democritus, Lavoisier, and Dalton, and understand their discoveries regarding the nature of atoms and chemical compounds.