Chapter 4: Atomic Structure Flashcards

Questions and Answers

What is an atom?

A particle that cannot exist independently

The smallest particle of an element that can retain its identity in a chemical reaction (correct)

A negatively charged particle in the nucleus

A chemical compound made of multiple elements

Who first suggested the idea of an atom and called it 'atomos'?

Democritus

Who discovered the electron?

J.J. Thomson

What is Dalton's Atomic Theory?

Different elements can chemically combine in whole number ratios. Signup and view all the answers

What does a scanning tunneling microscope do?

It can 'see' individual atoms. Signup and view all the answers

What are subatomic particles?

Particles smaller than atoms, including protons, neutrons, and electrons. Signup and view all the answers

What is the charge of electrons?

Negatively charged Signup and view all the answers

What is the charge of protons?

Positively charged Signup and view all the answers

What is a neutron?

A neutrally charged subatomic particle Signup and view all the answers

What is the plum-pudding model?

A model indicating electrons are embedded in a positive mass. Signup and view all the answers

What was the outcome of the gold-foil experiment conducted by Ernest Rutherford?

He discovered the existence of the nucleus. Signup and view all the answers

What is the atomic number?

The number of protons in an element Signup and view all the answers

What does mass number refer to?

The sum of protons and neutrons in an atom Signup and view all the answers

What is an isotope?

Atoms with the same number of protons but different numbers of neutrons Signup and view all the answers

Atomic mass is a simple average of all isotopes of an element.

False Signup and view all the answers

A ______ table is an arrangement of elements based on repeating properties.

periodic Signup and view all the answers

What defines the groups or families in the periodic table?

Vertical columns with similar properties Signup and view all the answers

What is the function of the anode?

Positively charged electrode Signup and view all the answers

What is the function of the cathode?

Negatively charged electrode Signup and view all the answers

Study Notes

Atomic Structure

Atoms are the basic units of elements, retaining their identity during chemical reactions.

Historical Contributors

Democritus: Proposed the concept of the atom as indivisible ('atomos'), favoring philosophical thought over experimental science.
John Dalton: Developed the first atomic theory detailing the nature of atoms, emphasizing that elements consist of indivisible particles and combine in fixed ratios during chemical reactions.

Dalton's Atomic Theory

All matter consists of tiny, indivisible particles called atoms.
Atoms of identical elements are the same, but differ from atoms of other elements.
Atoms can mix physically or chemically combine in simple whole-number ratios to form compounds.
Chemical reactions involve the separation, joining, or rearrangement of atoms; atoms cannot change into different elements.

Techniques and Discoveries

Scanning Tunneling Microscope: Allows visualization of individual atoms through graphical imaging.
Subatomic Particles: Atoms are composed of protons (positively charged), neutrons (neutral), and electrons (negatively charged).
J.J. Thomson: Identified electrons using a cathode-ray tube, proving their existence.
Robert A. Millikan: Measured the charge and calculated the mass of the electron (1/1840 of a hydrogen atom).
Eugen Goldstein: Discovered protons.
James Chadwick: Discovered neutrons.

Atomic Models

Thomson's Model: Known as the "plum-pudding model," which described electrons embedded in a positive charge.
Ernest Rutherford: Conducted the gold-foil experiment, establishing the existence of a dense nucleus within atoms. His model depicted electrons orbiting a central nucleus containing protons and neutrons.

Atomic Composition

Atomic Number: Number of protons in an atom, defining the element.
Mass Number: Total number of protons and neutrons in an atom.
Nuclide: Representation for an individual isotope.
Atomic Mass: Weighted average of an element's isotopes.
Isotopes: Variants of elements with the same number of protons but different numbers of neutrons.

Measurement and Classification

Atomic Mass Unit (amu): A unit based on 1/12 of a Carbon-12 atom, used for measuring atomic masses.
Periodic Table: Organized array of elements grouped by properties, reflecting periodic trends.
Periods: Horizontal rows where element properties vary across the table.
Groups/Families: Vertical columns indicating elements with similar properties.

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Test your knowledge of atomic structure with these flashcards. Each card features key terms and definitions essential for understanding the composition of matter, including the contributions of historical figures like Democritus and Dalton.