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Physical Science: Ch4: The Atom

___ is anything that has mass and takes up space. Matter
An ___ is a small particle that makes up all matter. atom
Atoms are mostly ___ space surrounding a massive central region of the atom called the___. empty, nucleus
Atoms contain ___ kinds of particles, two in the ___, and one outside the center of the atom. three, nucleus
In an atom’s nucleus, positively charged particles are ___. protons
A ___ is a neutral particle located in the nucleus of an atom. neutron
___ are negatively charged particles that move in the space outside an atom’s nucleus. Electrons
An electron has about ___ the mass of a neutron or proton. 1/2,000
The Greek philosopher ___ coined the word atom, based on the Greek word atoma,meaning “indivisible.” Democritus
Democritus proposed that atoms were small, ___ spheres. solid
The atom as Democritus described it was ___, meaning it was the smallest possible piece of matter that could not be cut into smaller pieces. indivisible
The French scientist Antoine ___ conducted experiments that led to the law ofconservation of ___. Lavoisier, mass
The law of ___ ___, uncovered by French chemist J. L. Proust, states that pure compounds always contain the same elements in the same proportions by mass. definite proportions
English schoolteacher and scientist ___ ___ did many experiments on gases that led to a new and more complete model of the atom. John Dalton
All ___ is made up of atoms. matter
Atoms are neither ___ nor ___ in chemical reactions. created, destroyed
___ of different elements combine in whole-number ratios. Atoms
Each element is made of a ___ type of atom. different
The atoms of different elements have different ___ and ___. masses, properties
Dalton used ___ to represent different elements, making it easier to write andcommunicate about the elements. symbols
In 1897, English scientist __ __ ______ discovered electrons while doing an experiment to see how ___ currents affected cathode rays. J. J. Thomson, electric
J. J. Thomson proposed a new ___ model to explain his observations: a solid spherethrough which ___ charge was spread evenly. atomic, positive
When two students of Ernest Rutherford shot ___ particles through gold foil, most passed straight through the foil, but some were scattered or even bounced ___ ___. alpha, straight back
Rutherford interpreted the unexpected results to mean that the alpha particles were hitting something with a ___ charge and a relatively large ___. positive, mass
Based on this information and further experiments, Rutherford developed a revised ___ of the atom. model
Rutherford’s model showed the atom as mostly ___ space, with the ___ in the middle. empty, nucleus
Rutherford discovered the positively charged particle, the ___, which is found in anatom’s nucleus proton
Rutherford predicted the existence of another particle, with ___ electric charge, in the nucleus of atoms. no
Rutherford’s model did not accurately explain how ___ are arranged in the atom. electrons
A Danish scientist, ___ ___, studied the hydrogen atom and then proposed a new model for the arrangement of electrons in an atom. Niels Bohr
A ___ ___ is a single wavelength of light that can be seen when the light from anexcited element is passed through a prism. spectral line
An ___ ___ is a region in space corresponding to a certain energy through which an electron moves. energy level
Bohr proposed that electrons moved in ___ around the nucleus. circles
Bohr thought that electrons fill the ___ energy levels of an atom first, and start filling the next energy level away from the ___ after an inner level is full. inner, nucleus
An element will react with other elements to try to receive a full ___ ___ ___. outer energy level
Bohr’s model of circular orbits for electrons did not explain the behavior of electrons in outer ___ ___. energy levels
Today, scientists think of an electron in an atom as being in an ___ ___, which is a region surrounding an atomic nucleus where an electron is ___ ___ to be found. electron cloud, most likely
An ___ is a pure substance that can be identified by the number of protons in the nucleus of its atoms. element
Each atom of a particular element has the same number of protons in its nucleus. Thisnumber is called the element’s ___ ___. atomic number
In a chart called the ___ ___ ___ ___ ___, elements are arranged horizontally by increasing atomic number and vertically in rows of elements with similar chemical properties. periodic table of the elements
Elements in the periodic table are metals, nonmetals, and ___. semimetals
All atoms of an element have the same number of ___. Different atoms of the sameelement can have different numbers of ___. protons, neutrons
The ___ ___ of an atom is the total number of neutrons and protons in the atom. mass number
Atoms of the same element that contain different numbers of neutrons are called ___. isotopes
Some isotopes of certain elements are ___, meaning they spontaneously decay and release particles and/or energy. radioactive
Hydrogen has three isotopes, called protium, ___, and ___. tritium, deuterium
The ___ ___ ___ of an element is the weighted average of the mixture of an element’s isotopes average atomic mass
An ___ is an atom that no longer is neutral because it has gained or lost electrons. ion
If an element loses an ___, it then has more protons than electrons and has a positive charge. An atom with a ___ charge is called a positive ion. electron, positive
When an atom gains an electron, it forms an ion with a ___ charge because it has more electrons than protons. The resulting ion is called a ___ ___. negative, negative ion
Created by: jnosik