Изотопы, ионы и масштаб ядра
Введено| English | Значение |
|---|---|
| mass number/mæs ˈnʌmbə/ | Массовое число |
| isotope/ˈaɪsətəʊp/ | Изотоп |
What would explain this observation?
- Two chlorine atoms can have the same proton number but different masses. Their nuclei contain different neutron numbers, while their element identity remains chlorine.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
Build the model
- A typical atom has radius about 0.1 nm, equal to 1×10⁻¹⁰ m. Its nucleus has a radius less than one ten-thousandth of the atom’s radius, of order 1×10⁻¹⁴ m. Almost all atomic mass is in the nucleus. Proton and neutron relative masses are each approximately one; an electron’s relative mass is very small. Mass number 质量数, A, counts protons plus neutrons. Isotopes 同位素 are atoms of the same element with different neutron numbers.
- isotope: Atoms of the same element with different numbers of neutrons; mass number: The total number of protons and neutrons in a nucleus.
Чем отличаются атомы хлора-35 и хлора-37?
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Изотопы имеют одинаковое протонное число — именно оно делает их одним и тем же элементом — и отличаются только количеством нейтронов, поэтому хлор-35 и хлор-37. Символ остается Cl.
Сопоставьте каждый технический термин с его точным определением.
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Используйте определения для различения смежных величин и процессов.
Choose evidence that can test it
- In nuclide notation the upper-left number is A and the lower-left is Z. Protons=Z; neutrons=A−Z. A neutral atom has Z electrons; a positive ion has lost electrons and a negative ion has gained them. Chlorine-35 and chlorine-37 both have Z=17, with 18 and 20 neutrons respectively. Their mass numbers differ without a change in proton number.
- Write a table with separate columns for A, Z, proton, neutron, electron and charge. Check A=protons+neutrons and charge=protons−electrons. For size comparisons convert radii into the same unit before dividing. A nucleus drawn clearly inside a circle is greatly enlarged relative to the atom; label the diagram not to scale and use numbers for a scale calculation.
Какие две привычки делают расследование или модель в данном случае более обоснованными?
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Указание условий и допущений позволяет другим точно воспроизвести работу, а фиксация подтверждающих данных даёт возможность проверить вывод. Сокрытие противоречащих результатов устраняет доказательства, способные оспорить ошибочный вывод, а одно измерение никогда не может обосновать более широкий claim.
Work from known quantities
- State the known values and their units. Choose the relation because its assumptions fit this case, then rearrange before substitution.
- Known: chlorine-37 as Cl⁻ has 17 protons, 37−17=20 neutrons and 17+1=18 electrons. In a scale model where atom radius is 1 m and nuclear radius is 1/10,000 of it, the nuclear radius is 0.0001 m = 0.1 mm. This illustrates the order of size, not a precise measured radius for every isotope.
A magnesium-25 atom has atomic number 12. How many neutrons does it contain? Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
Атом магния-25 имеет атомный номер 12. Сколько нейтронов он содержит?
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Результат: 13 нейтронов. Дано: магний-25; атомный номер 12. Число нейтронов = массовое число − атомный номер = 25 − 12 = 13 нейтронов. Количество протонов, 12, определяется элементом.
Check the conclusion and its limits
- Mass number is an integer particle count, whereas relative atomic mass is an abundance-weighted mean. Ions differ in electrons, isotopes in neutrons. Dividing two radii gives a length ratio; the volume ratio is different. Do not place neutrons outside the nucleus in a shell diagram.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
Different isotopes of an element have different proton numbers. This claim is false: Isotopes are defined as atoms of the SAME element - same proton number - with different neutron numbers. Different proton numbers would make them different elements, not isotopes.
Isotopes, ions and the scale of the nucleus: In nuclide notation the upper-left number is A and the lower-left is Z. Protons=Z; neutrons=A−Z. A neutral atom has Z electrons; a positive ion has lost electrons and a negative ion has gained them. Chlorine-35 and chlorine-37 both have Z=17, with 18 and 20 neutrons respectively. Their mass numbers differ without a change in proton number.
Разные изотопы одного элемента имеют разное число протонов.
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Изотопы — это атомы ОДНОГО элемента с одинаковым числом протонов, но разным числом нейтронов. Различное число протоков означало бы разные элементы, а не изотопы.
Атомы одного элемента с разным количеством нейтронов: запишите технический термин.
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изотоп означает Атомы одного элемента с разным количеством нейтронов.