El átomo

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Nombre
Clase
Fecha
Hoja de destrezas
Vocabulario y resumen de la sección
El átomo
VOCABULARIO
Define los siguientes términos en tus propias palabras. Usa el espacio en blanco
correspondiente.
1. protón
2. unidad de masa atómica
3. neutrón
4. número atómico
5. isótopo
6. número de masa
7. masa atómica
Copyright © by Holt, Rinehart and Winston. All rights reserved.
HOLT CIENCIAS Y TECNOLOGÍA
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Introducción a los átomos
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Nombre
Clase
Fecha
Vocabulario y resumen de la sección (continuación)
RESUMEN DE LA SECCIÓN
Lee el siguiente resumen de la sección.
•
Los átomos son extremadamente pequeños. Los objetos de tamaño normal están
formados por grandes cantidades de átomos.
•
Los átomos están formados por un núcleo, que tiene protones y a menudo neutrones, y
por electrones, que están en nubes de electrones alrededor del núcleo.
•
El número de protones del núcleo de un átomo es el número atómico de ese átomo.
Todos los átomos de un elemento tienen el mismo número atómico.
•
Los distintos isótopos de un elemento tienen en su núcleo un número diferente de
neutrones. Los isótopos de un elemento comparten la mayoría de las propiedades
químicas y físicas.
•
•
El número de masa de un átomo es la suma de los neutrones y los protones del átomo.
•
Las fuerzas que operan en un átomo son la fuerza gravitacional, la fuerza
electromagnética, la fuerza fuerte y la fuerza débil.
La masa atómica es un promedio ponderado de la masa de los isótopos naturales de
un elemento.
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HOLT CIENCIAS Y TECNOLOGÍA
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Introducción a los átomos
ANSWER KEY
Vocabulary and Section
Summary
5. He performed experiments and drew
SECTION: DEVELOPMENT OF THE
ATOMIC THEORY
6.
1. atom: the smallest unit of an element
that maintains the properties of an
element
2. electron: a subatomic particle that has
a negative charge
3. nucleus: in physical science, an atom’s
central region, which is made up of
protons and neutrons
4. electron cloud: a region around the
nucleus of an atom where electrons
are likely to be found
7.
8.
SECTION: THE ATOM
1. proton: a subatomic particle that has a
2.
3.
4.
5.
6.
7.
9.
positive charge and that is found in
the nucleus of an atom
atomic mass unit: a unit of mass that
describes the mass of an atom or
molecule
neutron: a subatomic particle that has
no charge and that is found in the
nucleus of an atom
atomic number: the number of protons
in the nucleus of an atom; the atomic
number is the same for all atoms of an
element
isotope: an atom that has the same
number of protons (or the same atomic
number) as other atoms of the same
element do but that has a different
number of neutrons (and thus a
different atomic mass)
mass number: the sum of the numbers
of protons and neutrons in the nucleus
of an atom
atomic mass: the mass of an atom
expressed in atomic mass units
10.
conclusions from them to develop his
theory.
Rutherford’s gold foil experiment, in
which Rutherford observed that most
of the positively charged particles that
he aimed at a piece of gold foil went
straight through
Bohr suggested that electrons could
move around the nucleus only in certain paths. They could jump from path
to path, but not stay between the
paths.
Bohr’s theory held that electrons can
travel only in certain paths around the
nucleus. The current atomic theory is
that electrons travel in regions where
they are likely to be found.
Rutherford placed a surface behind
the gold foil, which would glow where
the positively charged particles hit it.
This shows that he was trying to find
out where the particles went after
hitting the gold foil.
The model represents electrons as
mixed throughout an atom. Rutherford
showed this arrangement to be
incorrect.
SECTION: THE ATOM
1. Sample answer: Different isotopes
2.
3.
4.
5.
Section Review
SECTION: DEVELOPMENT OF THE
ATOMIC THEORY
6.
1. Sample answer: the smallest part of an
7.
element that has the properties of that
element
2. electron
3. nucleus
4. B
8.
have the same number of protons but
different numbers of neutrons.
atomic number
atomic mass
B
Gravitational force acts between
objects based on their mass.
Electromagnetic force attracts objects
of opposite electric charge and repels
objects of the same electric charge.
The strong force holds the protons
and neutrons of atomic nuclei
together. The weak force plays a role
in radioactive decay.
(0.30 203 amu) (0.70 205 amu) 204.4 amu
Gravitational force in the nucleus is so
small because the masses of nuclear
particles are so small.
no; Without neutrons, two protons
brought into close contact would repel
each other.
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Holt Science and Technology
62
Introduction to Atoms