Санкт-петербургского государственного университета высшее профессиональное образование т. А. Степанова, И. Ю. Ступина
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Упр. 1. Назовите значения следующих интернациональных слов: conduct, electricity, indication, orbital, spin, energy, control, confi guration, stability, characteristic Упр. 2. Определите значения выделенных слов по контексту’. 1. We saw her on the opposite side of the street and crossed the street to meet her. 2. In terms of modem chcmistry it is more correct to speak about the clcctronic levels than clcctronic shells. 3. The main duty of a student is to study. Слова к тексту: loose— высвобождать; desire— желать; g o a l— цель; seek— искать, стре миться; in tu r n — в свою очередь 140 Text 20 В Прочтите текст про себя (контрольное время чтения — 3 минуты). Covalcncc Many compound substanccs do not have particularly high melting and boiling points, do not conduct clcctricity when they arc molten, and, thus, give no indication o f being ionic. The particles o f such compounds are molcculcs. In these, any bond between two atoms is believed to be a pair o f shared electrons, as it was suggested originally by the American chcmist G. N. Lewis. The electrons o f such a shared pair occupy a single orbital and spin in opposite directions. Atoms entering such unions arc said to cxibit covalcncc and the bonds thus formed are described as covalcnt. When two or more atoms share electrons to form molcculcs, all the electrons of the several atoms involved* bccomc common property and arc distributed among energy levels and orbitals characteristic of the molcculcs. A simpler treatment than this method o f molccular orbitals is that of atomic orbitals. By it. cach atom in the molcculc is treated as if it controlled all its own electrons except those shared with another atom. The shared electrons arc treated as common to both. The carbon atom has two electrons in its first main energy level and four in its second. To obtain a noblc-gas configuration it would have to loose or gain 4 electrons. Sincc it can do neither, it approaches the desired _ goal as nearly as possible by sharing its 4 electrons with atoms that also seek greater stability and will, in turn, share some o f their valcncc electrons with it. Упр. 3. Передайте основное содержание текста в нескольких пред- ^ ложеннях. Упр. 4. Составьте план текста. Упр. 5. Прочтите предложения и скажите, соответствуют лн они содержанию текста. Если нет, исправьте их. 1. Not all compound substanccs conduct clcctricity when they arc molten. 2. Lewis studied the bond formed by a pair of shared electrons. 3. The bond is described as covalcnt if the electrons of a shared pair occupy a single orbital and spin in opposite directions. 4. The method o f atomic orbitals is more complex than that o f molccular orbitals. 5. The shared electrons arc believed to belong to one of the two bounded atoms. 6. To obtain a noblc-gas configuration the carbon atom has to loose 4 electrons. * (h e sev eral a to m s involved — несколько участвую щ их атомов 141 Упр. б. Найдите в тексте описание того, кар распределяются элект роны при образовании связи с участием углеродного атома, и переве дите этот отрывок на русский язык. жүктеу/скачать 5,96 Mb. Достарыңызбен бөлісу:
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